Big-Data-HPC-Platform/ecl/hqlcpp/hqlcppds.cpp

/*##############################################################################

    Copyright (C) 2011 HPCC Systems.

    All rights reserved. This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
############################################################################## */
#include "jliball.hpp"
#include "hql.hpp"

#include "platform.h"
#include "jlib.hpp"
#include "jmisc.hpp"
#include "jstream.ipp"
#include "jdebug.hpp"

#include "hql.hpp"
#include "hqlthql.hpp"
#include "hqlhtcpp.ipp"
#include "hqlttcpp.ipp"
#include "hqlutil.hpp"
#include "hqlthql.hpp"
#include "hqlpmap.hpp"
#include "hqlattr.hpp"

#include "hqlwcpp.hpp"
#include "hqlcpputil.hpp"
#include "hqltcppc.ipp"
#include "hqlopt.hpp"
#include "hqlfold.hpp"
#include "hqlcerrors.hpp"
#include "hqlcatom.hpp"
#include "hqlresource.hpp"
#include "hqlregex.ipp"
#include "hqlsource.ipp"
#include "hqlcse.ipp"
#include "hqlgraph.ipp"
#include "hqlccommon.hpp"
#include "hqliter.ipp"
#include "hqlinline.hpp"
#include "hqlusage.hpp"

#define MAX_FIXED_SIZE_RAW 1024
#define INLINE_TABLE_EXPAND_LIMIT 4

void addGraphIdAttribute(ActivityInstance * instance, BuildCtx & ctx, IHqlExpression * graphId)
{
    SubGraphInfo * match = matchActiveGraph(ctx, graphId);
    assertex(match);
    instance->addAttributeInt("_graphId", match->graphId);
}

//===========================================================================


void HqlCppTranslator::doBuildRowIfBranch(BuildCtx & initctx, BuildCtx & ctx, BoundRow * targetRow, IHqlExpression * branchExpr)
{
    IHqlExpression * targetRowExpr = targetRow->queryBound();

    Owned<IReferenceSelector> rowSelector = buildNewRow(ctx, branchExpr);
    Owned<BoundRow> boundRow = rowSelector->getRow(ctx);
    OwnedHqlExpr rowExpr = getPointer(boundRow->queryBound());
    OwnedHqlExpr castRow = createValue(no_implicitcast, targetRowExpr->getType(), LINK(rowExpr));
    ctx.addAssign(targetRowExpr, castRow);

    if (rowSelector->isConditional())
        targetRow->setConditional(true);
}


IReferenceSelector * HqlCppTranslator::doBuildRowIf(BuildCtx & ctx, IHqlExpression * expr)
{
    OwnedHqlExpr foldedCond = foldHqlExpression(expr->queryChild(0));
    if (foldedCond->queryValue())
    {
        unsigned branch = (foldedCond->queryValue()->getBoolValue()) ? 1 : 2;
        return buildNewRow(ctx, expr->queryChild(branch));
    }

    IHqlExpression * trueBranch = expr->queryChild(1);
    IHqlExpression * falseBranch = expr->queryChild(2);

    //Ideally should have a constant modifier on the following row...
    Owned<ITypeInfo> rowType = makeReferenceModifier(expr->getType());
    OwnedHqlExpr rowExpr = ctx.getTempDeclare(rowType, NULL);
    Owned<BoundRow> row = createBoundRow(expr->queryBody(), rowExpr);

    //MORE: Need casts because cursor may be (probably are) constant, but temporary isn't
    //should find out by looking at the a const modifier on the cursor.
    BuildCtx condctx(ctx);

    IHqlStmt * cond = buildFilterViaExpr(condctx, foldedCond);
    //Mark the context as conditional after the filter test, so any temporaries from the filter aren't affected.
    condctx.associateExpr(queryConditionalRowMarker(), rowExpr);

    doBuildRowIfBranch(ctx, condctx, row, trueBranch);

    condctx.selectElse(cond);

    condctx.associateExpr(queryConditionalRowMarker(), rowExpr);
    doBuildRowIfBranch(ctx, condctx, row, falseBranch);

    ctx.associate(*row);
    return createReferenceSelector(row);
}


IReferenceSelector * HqlCppTranslator::doBuildRowDeserializeRow(BuildCtx & ctx, IHqlExpression * expr)
{
    IHqlExpression * srcRow = expr->queryChild(0);
    IHqlExpression * record = expr->queryRecord();

    Owned<BoundRow> tempRow = declareLinkedRow(ctx, expr, false);

    CHqlBoundTarget target;
    target.expr.set(tempRow->queryBound());

    HqlExprArray args;  
    args.append(*createRowAllocator(ctx, record));
    args.append(*createRowSerializer(ctx, record, deserializerAtom));
    args.append(*LINK(srcRow));
    Owned<ITypeInfo> resultType = makeReferenceModifier(makeAttributeModifier(makeRowType(record->getType()), getLinkCountedAttr()));
    OwnedHqlExpr call = bindFunctionCall(rtlDeserializeRowAtom, args, resultType);
    buildExprAssign(ctx, target, call);

    ctx.associate(*tempRow);
    return createReferenceSelector(tempRow);
}


void HqlCppTranslator::buildConstRow(IHqlExpression * record, IHqlExpression * rowData, CHqlBoundExpr & bound)
{
    OwnedHqlExpr marker = createAttribute(rowAtom, LINK(record), LINK(rowData));
    BuildCtx declareCtx(*code, literalAtom);
    if (declareCtx.getMatchExpr(marker, bound))
        return;

    //MORE: This probably needs to go in the header as well...
    Owned<ITypeInfo> rowType = makeConstantModifier(makeRowType(record->getType()));

    StringBuffer rowName;
    getUniqueId(rowName.append("r"));

    //Generate two variables to cope with the different ways the data is interpreted.
    //Would prefer it to be cleaner... row value would need an associated size
    unsigned dataSize = rowData->queryType()->getSize();
    OwnedITypeInfo declareType;
    OwnedHqlExpr initializer;
    if (options.staticRowsUseStringInitializer)
    {
        //Generates smaller code (and probably more efficient representation in the c++ compiler
        //const byte[5+1] = "Hello";         need an extra byte for the implicit \0
        declareType.setown(makeDataType(dataSize+1));
        initializer.set(rowData);
    }
    else
    {
        //Following is strictly correct, but much larger.
        //const byte[5] = { 'H','e','l','l','o' };
        declareType.set(rowData->queryType());
        initializer.setown(createValue(no_create_initializer, rowData->getType(), LINK(rowData)));
    }

    //MORE: Currently these are marked as const rows, but not generated as such 
    OwnedHqlExpr boundDeclare = createVariable(rowName, makeConstantModifier(LINK(declareType)));
    OwnedHqlExpr boundRow = createVariable(rowName, LINK(rowType));
    declareCtx.addDeclare(boundDeclare, initializer);

    if (options.spanMultipleCpp)
    {
        BuildCtx protoctx(*code, mainprototypesAtom);
        protoctx.addDeclareExternal(boundDeclare);
    }

    bound.length.setown(getSizetConstant(dataSize));
    bound.expr.set(boundRow);
    declareCtx.associateExpr(marker, bound);
}


bool HqlCppTranslator::doBuildRowConstantTransform(IHqlExpression * transform, CHqlBoundExpr & bound)
{
    if (!transform->isConstant() || !options.generateStaticInlineTables)
        return false;
    OwnedHqlExpr constRow = createConstantRowExpr(transform);
    if (!constRow || !canGenerateStringInline(constRow->queryType()->getSize()))
        return false;
    buildConstRow(transform->queryRecord(), constRow, bound);
    return true;
}


IReferenceSelector * HqlCppTranslator::doBuildRowCreateRow(BuildCtx & ctx, IHqlExpression * expr)
{
    CHqlBoundExpr bound;
    if (!doBuildRowConstantTransform(expr->queryChild(0), bound))
        return doBuildRowViaTemp(ctx, expr);
    BoundRow * row = bindConstantRow(ctx, expr, bound);
    return createReferenceSelector(row);
}

BoundRow * HqlCppTranslator::bindConstantRow(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & bound)
{
    BoundRow * row = bindRow(ctx, expr, bound.expr);
    //MORE: This should be done more cleanly
    OwnedHqlExpr sizeOfRow = createSizeof(row->querySelector());
    ctx.associateExpr(sizeOfRow, bound.length);
    return row;
}

bool HqlCppTranslator::doBuildRowConstantNull(IHqlExpression * expr, CHqlBoundExpr & bound)
{
    if (!options.generateStaticInlineTables)
        return false;

    IHqlExpression * record = expr->queryRecord();
    OwnedHqlExpr constRow = createConstantNullRowExpr(record);
    if (!constRow)
        return false;

    buildConstRow(record, constRow, bound);
    return true;
}


IReferenceSelector * HqlCppTranslator::doBuildRowNull(BuildCtx & ctx, IHqlExpression * expr)
{
    CHqlBoundExpr bound;
    if (!doBuildRowConstantNull(expr, bound))
        return doBuildRowViaTemp(ctx, expr);

    BoundRow * row = bindRow(ctx, expr, bound.expr);
    return createReferenceSelector(row);
}


IReferenceSelector * HqlCppTranslator::doBuildRowViaTemp(BuildCtx & ctx, IHqlExpression * expr)
{
    HqlExprAssociation * match;
    if (expr->isDataset())
        match = ctx.queryAssociation(expr->queryNormalizedSelector(), AssocCursor, NULL);
    else
        match = ctx.queryAssociation(expr, AssocRow, NULL);

    if (match)
    {
        BoundRow * row = (BoundRow *)match;
        return createReferenceSelector(row, expr);
    }

    Owned<BoundRow> tempRow = declareTempRow(ctx, ctx, expr);

    Owned<BoundRow> rowBuilder = createRowBuilder(ctx, tempRow);
    Owned<IReferenceSelector> createdRef = createReferenceSelector(rowBuilder);
    buildRowAssign(ctx, createdRef, expr);
    finalizeTempRow(ctx, tempRow, rowBuilder);

    ctx.associate(*tempRow);
    return createReferenceSelector(tempRow);
}


void HqlCppTranslator::buildDefaultRow(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & bound)
{
    OwnedHqlExpr clearExpr = createRow(no_null, LINK(expr->queryRecord()), createAttribute(clearAtom));
    BoundRow * matchedRow = (BoundRow *)ctx.queryAssociation(clearExpr, AssocRow, NULL);
    if (!matchedRow)
    {
        if (doBuildRowConstantNull(expr, bound))
        {
            bindRow(ctx, clearExpr, bound.expr);
        }
        else
        {
            BuildCtx * declarectx = &ctx;
            BuildCtx * callCtx = &ctx;
            getInvariantMemberContext(ctx, &declarectx, &callCtx, true, false);

            Owned<BoundRow> tempRow = declareTempRow(*declarectx, *callCtx, clearExpr);

            Owned<BoundRow> rowBuilder = createRowBuilder(*callCtx, tempRow);
            OwnedHqlExpr size = createVariable(LINK(sizetType));
            OwnedHqlExpr clearCall = createClearRowCall(*callCtx, rowBuilder);
            callCtx->addDeclare(size, clearCall);

            OwnedHqlExpr sizeOfRow = createSizeof(rowBuilder->querySelector());
            callCtx->associateExpr(sizeOfRow, size);
            finalizeTempRow(*callCtx, tempRow, rowBuilder);
            declarectx->associate(*tempRow);

            bound.expr.set(tempRow->queryBound());
        }
    }
    else
        bound.expr.set(matchedRow->queryBound());

    //yuk yuk, hack.  If called from a const context then need to make the reference unconst.
    //The real fix is to implement real const tracking throughout the code generator, but that is far from trivial.
    //rkc39.hql is an example...
    if (ctx.queryMatchExpr(constantMemberMarkerExpr))
        bound.expr.setown(createValue(no_cast, makeReferenceModifier(bound.expr->getType()), getPointer(bound.expr)));
}

void HqlCppTranslator::buildNullRow(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & bound)
{
    bound.expr.setown(createValue(no_nullptr, makeRowReferenceType(expr)));
}

IReferenceSelector * HqlCppTranslator::doBuildRowFromXML(BuildCtx & ctx, IHqlExpression * expr)
{
//  assertex(supportsLinkCountedRows);
    Owned<ITypeInfo> overrideType = setLinkCountedAttr(expr->queryType(), true);
    Owned<ITypeInfo> utf8Type = makeUtf8Type(UNKNOWN_LENGTH, NULL);
    IHqlExpression * record = expr->queryRecord();
    OwnedHqlExpr ds = createDataset(no_anon, LINK(record));

    StringBuffer xmlInstanceName, xmlFactoryName, s;
    bool usesContents = false;
    getUniqueId(xmlInstanceName.append("xml"));
    buildXmlReadTransform(ds, xmlFactoryName, usesContents);
    OwnedHqlExpr curActivityId = getCurrentActivityId(ctx);
    s.append("Owned<IXmlToRowTransformer> ").append(xmlInstanceName).append(" = ").append(xmlFactoryName).append("(ctx,");
    generateExprCpp(s, curActivityId).append(");");
    ctx.addQuoted(s);

    HqlExprArray args;
    args.append(*createRowAllocator(ctx, record));
    args.append(*ensureExprType(expr->queryChild(1), utf8Type));
    args.append(*createQuoted(xmlInstanceName, makeBoolType()));
    args.append(*createConstant(expr->hasProperty(trimAtom)));
    OwnedHqlExpr function = bindFunctionCall(createRowFromXmlAtom, args, overrideType);

    CHqlBoundExpr bound;
    buildExpr(ctx, function, bound);

    Owned<ITypeInfo> rowType = makeReferenceModifier(LINK(overrideType));
    OwnedHqlExpr rowExpr = ctx.getTempDeclare(rowType, NULL);
    Owned<BoundRow> row = createBoundRow(expr, rowExpr);
    ctx.associate(*row);                                    // associate here because it is compared inside the loop

    OwnedHqlExpr defaultRowPtr = getPointer(bound.expr);
    ctx.addAssign(rowExpr, defaultRowPtr);

    return createReferenceSelector(row);
}




//NB: If this is a dataset operation, this function assumes that any parent datasets are already in scope 
//    i.e. processed in buildDatasetAssign()
//    the one exception is aggregate because it needs to treat its input differently.

IReferenceSelector * HqlCppTranslator::buildNewOrActiveRow(BuildCtx & ctx, IHqlExpression * expr, bool isNew)
{
    if (isNew)
        return buildNewRow(ctx, expr);
    else
        return buildActiveRow(ctx, expr);
}


IReferenceSelector * HqlCppTranslator::buildNewRow(BuildCtx & ctx, IHqlExpression * expr)
{
    assertex(!expr->isDataset());
    BoundRow * match = static_cast<BoundRow *>(ctx.queryAssociation(expr, AssocRow, NULL));
    if (match)
        return createReferenceSelector(match, expr);

    BoundRow * row = NULL;
    node_operator op = expr->getOperator();
    switch (op)
    {
    case no_activerow:
        return buildActiveRow(ctx, expr->queryChild(0));
    case no_if:
        return doBuildRowIf(ctx, expr);
    case no_id2blob:
        return doBuildRowIdToBlob(ctx, expr, true);
    case no_index:
    case no_selectnth:
        return buildDatasetIndex(ctx, expr);
    case no_left:
    case no_right:
    case no_self:
    case no_top:
    case no_activetable:
        return buildActiveRow(ctx, expr);
    case no_fromxml:
        return doBuildRowFromXML(ctx, expr);
    case no_serialize:
        if (isDummySerializeDeserialize(expr))
            return buildNewRow(ctx, expr->queryChild(0)->queryChild(0));
        return doBuildRowViaTemp(ctx, expr);
    case no_deserialize:
        if (isDummySerializeDeserialize(expr))
            return buildNewRow(ctx, expr->queryChild(0)->queryChild(0));
        return doBuildRowDeserializeRow(ctx, expr);
    case no_deref:
        {
            //Untested
            CHqlBoundExpr bound;
            buildExpr(ctx, expr, bound);
            row = bindRow(ctx, expr, bound.expr);
            break;
        }
    case no_createrow:
        return doBuildRowCreateRow(ctx, expr);
    case no_newusertable:
    case no_hqlproject:
    case no_temprow:
    case no_projectrow:
        return doBuildRowViaTemp(ctx, expr);
    case no_null:
        return doBuildRowNull(ctx, expr);
    case no_typetransfer:
        {
            CHqlBoundExpr bound;
            IHqlExpression * value = expr->queryChild(1);
            if (value->isDatarow())
                buildAddress(ctx, value, bound);
            else
                buildExpr(ctx, value, bound);

            OwnedHqlExpr cursorExpr = createValue(no_implicitcast, makeReferenceModifier(expr->getType()), LINK(bound.expr));
            row = bindRow(ctx, expr, cursorExpr);
            break;
        }
    case no_getresult:
        {
            IHqlExpression * seqAttr = expr->queryProperty(sequenceAtom);
            IHqlExpression * nameAttr = expr->queryProperty(namedAtom);
            IHqlExpression * record = expr->queryRecord();
            OwnedHqlExpr serializedRecord = getSerializedForm(record);

            OwnedHqlExpr temp = createDatasetF(no_getresult, LINK(serializedRecord), LINK(seqAttr), LINK(nameAttr), NULL);
            OwnedHqlExpr row = createRow(no_selectnth, LINK(temp), createComma(getSizetConstant(1), createAttribute(noBoundCheckAtom)));
            row.setown(ensureDeserialized(row, expr->queryType()));
            return buildNewRow(ctx, row);
        }
    case no_matchattr:
        return doBuildRowMatchAttr(ctx, expr);
    case no_matchrow:
        return doBuildRowMatchRow(ctx, expr, true);
    case no_getgraphresult:
    case no_call:
    case no_externalcall:
    case no_alias:
    case no_translated:
    case no_libraryinput:
        {
            CHqlBoundExpr bound;
            buildExpr(ctx, expr, bound);

            Owned<ITypeInfo> rawType = removeModifier(expr->queryType(), typemod_ref);
            OwnedHqlExpr cursorExpr = createValue(no_implicitcast, makeReferenceModifier(LINK(rawType)), LINK(bound.expr));
            row = bindRow(ctx, expr, cursorExpr);
            if (bound.length)
            {
                OwnedHqlExpr sizeOfRow = createSizeof(row->querySelector());
                ctx.associateExpr(sizeOfRow, bound.length);
            }

            //We could associate the original expression to allow better cse for child datasets in transforms, but it doesn't actually improve any examples
            //IHqlExpression * original = queryPropertyChild(expr, _original_Atom, 0);
            //if (original)
            //  bindRow(ctx, original, cursorExpr)->setResultAlias();
            break;//return createReferenceSelector(cursor);
        }
    case no_comma:
    case no_compound:
        buildStmt(ctx, expr->queryChild(0));
        return buildNewRow(ctx, expr->queryChild(1));
    case no_select:
        {
#ifdef _DEBUG
            IHqlExpression * field = expr->queryChild(1);
#endif
            Owned<IReferenceSelector> selector;
            if (isNewSelector(expr))
                selector.setown(buildNewRow(ctx, expr->queryChild(0)));
            else
                selector.setown(buildActiveRow(ctx, expr->queryChild(0)));
            return selector->select(ctx, expr);
        }
        //If called because known to be a single row.
    case no_datasetfromrow:
    case no_nofold:
    case no_nohoist:
    case no_section:
    case no_sectioninput:
        return buildNewRow(ctx, expr->queryChild(0));
    case no_skip:
        {
            buildStmt(ctx, expr);
            OwnedHqlExpr null = createNullExpr(expr);
            return buildNewRow(ctx, null);
        }
    case no_alias_scope:
        {
            expandAliasScope(ctx, expr);
            return buildNewRow(ctx, expr->queryChild(0));
        }
    case no_split:
        throwUnexpected();
        //not at all sure about this.....
        return buildNewRow(ctx, expr->queryChild(0));
    default:
        {
            HqlExprAssociation * match;
            if (expr->isDataset())
                match = ctx.queryAssociation(expr->queryNormalizedSelector(), AssocCursor, NULL);
            else
                match = ctx.queryAssociation(expr, AssocRow, NULL);

            if (match)
            {
                BoundRow * row = (BoundRow *)match;
                IReferenceSelector * alias = row->queryAlias();
                if (alias)
                    return LINK(alias);
                return createReferenceSelector(row, expr);
            }
            UNIMPLEMENTED_XY("row", getOpString(expr->getOperator()));
        }
    }

    assertex(row);
    return createReferenceSelector(row);
}


IReferenceSelector * HqlCppTranslator::buildActiveRow(BuildCtx & ctx, IHqlExpression * expr)
{
    node_operator op = expr->getOperator();
    switch (op)
    {
    case no_left:
    case no_right:
    case no_self:
    case no_top:
    case no_activetable:
    case no_selfref:            // shouldn't ever occur...
        //All selectors should be listed here...
        break;
    case no_activerow:
        return buildActiveRow(ctx, expr->queryChild(0));
    default:
        if (!expr->isDataset())
            return buildNewRow(ctx, expr);
        break;
    }

    HqlExprAssociation * match = ctx.queryAssociation(expr->queryNormalizedSelector(), AssocCursor, NULL);
    if (match)
    {
        BoundRow * row = (BoundRow *)match;
        IReferenceSelector * alias = row->queryAlias();
        if (alias)
            return LINK(alias);
        return createReferenceSelector(row, expr);
    }

    switch (op)
    {
    case no_select:
        {
#ifdef _DEBUG
            IHqlExpression * field = expr->queryChild(1);
#endif
            Owned<IReferenceSelector> selector = buildNewOrActiveRow(ctx, expr->queryChild(0), isNewSelector(expr));
            return selector->select(ctx, expr);
        }
    case no_id2blob:
        return doBuildRowIdToBlob(ctx, expr, false);
    }

    StringBuffer tablename;
    getExprIdentifier(tablename, expr);

    traceExpression("Dataset not found", expr);

    RowAssociationIterator iter(ctx);
    ForEach(iter)
    {
        BoundRow & cur = iter.get();
        traceExpression("BoundCursor:", cur.querySelector());
    }
    throwError1(HQLERR_DatasetNotActive, tablename.str());
    return NULL; //remove warning about control paths
}


//---------------------------------------------------------------------------

void HqlCppTranslator::doBuildExprAggregate(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt)
{
    OwnedHqlExpr normalized = normalizeAnyDatasetAliases(expr);
    if (expr != normalized)
    {
        buildExpr(ctx, normalized, tgt);
        return;
    }

    node_operator op = expr->getOperator();
    ITypeInfo * type = expr->queryType();
    ITypeInfo * tempType = op == no_count ? unsignedType : type;

    LoopInvariantHelper helper;
    BuildCtx aggctx(ctx);
    if (options.optimizeLoopInvariant)
        helper.getBestContext(aggctx, expr);

    CHqlBoundTarget result;
    createTempFor(aggctx, tempType, result, typemod_none, FormatNatural);
    doBuildAssignAggregate(aggctx, result, expr);

    tgt.setFromTarget(result);
    if (!isSameBasicType(type, tempType))
        tgt.expr.setown(createValue(no_implicitcast, LINK(type), tgt.expr.getClear()));
    if (expr->isPure())
        aggctx.associateExpr(expr, tgt);
}


void HqlCppTranslator::doBuildAssignAggregateLoop(BuildCtx & ctx, const CHqlBoundTarget & target, IHqlExpression * expr, IHqlExpression * dataset, IHqlExpression * doneFirstVar)
{
    node_operator op = expr->getOperator();
    switch (op)
    {
    case no_exists:
        {
            OwnedHqlExpr optimized = queryOptimizedExists(ctx, expr, dataset);
            if (optimized)
            {
                assignBound(ctx, target, optimized);
                return;
            }
            break;
        }
    case no_count:
        {
            CHqlBoundExpr temp;
            if (canBuildOptimizedCount(ctx, dataset, temp))
            {
                OwnedHqlExpr thisCount = temp.getTranslatedExpr();
                buildIncrementAssign(ctx, target, thisCount);
                return;
            }
            break;
        }
    }

    switch (dataset->getOperator())
    {
    case no_if:
        {
            BuildCtx subctx(ctx);
            IHqlStmt * stmt = buildFilterViaExpr(subctx, dataset->queryChild(0));
            doBuildAssignAggregateLoop(subctx, target, expr, dataset->queryChild(1), doneFirstVar);
            subctx.selectElse(stmt);
            doBuildAssignAggregateLoop(subctx, target, expr, dataset->queryChild(2), doneFirstVar);
            return;
        }
    case no_addfiles:
        {
            doBuildAssignAggregateLoop(ctx, target, expr, dataset->queryChild(0), doneFirstVar);
            doBuildAssignAggregateLoop(ctx, target, expr, dataset->queryChild(1), doneFirstVar);
            return;
        }
    case no_null:
        return;
    }

    LinkedHqlExpr arg = expr->queryChild(1);
    IHqlExpression * oldDataset = expr->queryChild(0);
    //If no_if or no_addfiles has been optimized above then the selector for the argument will have changed => map it.
    if (arg && (dataset != oldDataset))
        arg.setown(replaceSelector(arg, oldDataset, dataset));

    bool needToBreak = (op == no_exists);
    if (needToBreak)
    {
        //if it can have at most one row (fairly strange code!) then don't add a break
        //unless it was deliberately a choosen to restrict the number of iterations.
        if (hasNoMoreRowsThan(dataset, 1) && (dataset->getOperator() != no_choosen))
            needToBreak = false;
    }

    BuildCtx loopctx(ctx);
    buildDatasetIterate(loopctx, dataset, needToBreak);

    switch (op)
    {
    case no_exists:
        buildExprAssign(loopctx, target, queryBoolExpr(true));
        if (needToBreak)
            loopctx.addBreak();
        break;
    case no_count:
        {
            OwnedHqlExpr inc = createValue(no_postinc, makeVoidType(), LINK(target.expr));
            loopctx.addExpr(inc);
            break;
        }
    case no_sum:
        {
            OwnedHqlExpr cseArg = options.spotCSE ? spotScalarCSE(arg) : LINK(arg);
            buildIncrementAssign(loopctx, target, cseArg);
            break;
        }
    case no_min:
    case no_max:
        {
            BuildCtx maxctx(loopctx);
            OwnedHqlExpr resultExpr = target.getTranslatedExpr();

            OwnedHqlExpr cseArg = options.spotCSE ? spotScalarCSE(arg) : LINK(arg);
            OwnedHqlExpr simpleArg = buildSimplifyExpr(loopctx, cseArg);
            OwnedHqlExpr test = createBoolExpr((op == no_min) ? no_lt : no_gt, LINK(simpleArg), LINK(resultExpr));
            if (doneFirstVar)
            {
                IHqlExpression * firstTest = createValue(no_not, makeBoolType(), LINK(doneFirstVar));
                test.setown(createBoolExpr(no_or, firstTest, test.getClear()));
            }
            buildFilter(maxctx, test);

            buildExprAssign(maxctx, target, simpleArg);
            if (doneFirstVar)
                buildAssignToTemp(maxctx, doneFirstVar, queryBoolExpr(true));
            break;
        }
    default:
        assertex(!"unknown aggregate on child datasets");
        break;
    }
}

bool assignAggregateDirect(const CHqlBoundTarget & target, IHqlExpression * expr)
{
    node_operator op = expr->getOperator();
    ITypeInfo * type = expr->queryType();
    ITypeInfo * tempType = op == no_count ? unsignedType : type;

    if (!isSameUnqualifiedType(target.queryType(), tempType))
        return false;

    //For exists/count/sum use a temporary variable, and then assign rather than accumulating directly in the target
    switch (op)
    {
    case no_sum:
        if (type->getTypeCode() != type_int)
            break;
        //fall through
    case no_exists:
    case no_count:
        if (target.expr->getOperator() != no_variable)
            return false;
        break;
    }
    return true;
}

static bool isNullValueMinimumValue(ITypeInfo * type)
{
    switch (type->getTypeCode())
    {
    case type_int:
    case type_swapint:
    case type_decimal:
        return !type->isSigned();
    case type_data:
    case type_qstring:
        return true;
    }
    return false;
}

void HqlCppTranslator::doBuildAssignAggregate(BuildCtx & ctx, const CHqlBoundTarget & target, IHqlExpression * _expr)
{
    OwnedHqlExpr expr = normalizeAnyDatasetAliases(_expr);
    if (assignAggregateDirect(target, expr))
    {
        IHqlExpression * dataset = expr->queryChild(0);
        OwnedHqlExpr resultExpr = target.getTranslatedExpr();

        node_operator op = expr->getOperator();
        switch (op)
        {
        case no_exists:
            buildExprAssign(ctx, target, queryBoolExpr(false));
            break;
        default:
            {
                OwnedHqlExpr null = createNullExpr(target.queryType());
                buildExprAssign(ctx, target, null);
                break;
            }
        }

        OwnedHqlExpr doneFirstVar;
        if ((op == no_min) || ((op == no_max) && !isNullValueMinimumValue(target.queryType())))
        {
            doneFirstVar.setown(ctx.getTempDeclare(queryBoolType(), queryBoolExpr(false)));
        }

        doBuildAssignAggregateLoop(ctx, target, expr, dataset, doneFirstVar);
    }
    else
    {
        doBuildExprAssign(ctx, target, expr);
    }
}


//---------------------------------------------------------------------------

bool HqlCppTranslator::canBuildOptimizedCount(BuildCtx & ctx, IHqlExpression * dataset, CHqlBoundExpr & tgt)
{
    switch (dataset->getOperator())
    {
    case no_select:
        {
            if (isMultiLevelDatasetSelector(dataset, false))
                return false;

            Owned<IReferenceSelector> selector = buildReference(ctx, dataset);
            CHqlBoundExpr temp;
            selector->get(ctx, temp);
            tgt.expr.setown(getBoundCount(temp));
            return true;
        }
        break;
    default:
        if (!options.tempDatasetsUseLinkedRows)
            break;
        if (!alwaysEvaluatesToBound(dataset))
            break;
        //fall through
    case no_rows:
    case no_null:
        {
            CHqlBoundExpr temp;
            buildDataset(ctx, dataset, temp, FormatNatural);
            tgt.expr.setown(getBoundCount(temp));
            return true;
        }
    }

#if 0
    //This is improves a few obscure cases (normally in the global context).  I'm not convinced it is worth the extra cycles.
    //Could also remove the bound.count test.
    CHqlBoundExpr bound;
    if (ctx.getMatchExpr(dataset, bound) && bound.count)
    {
        tgt.expr.setown(getBoundCount(bound));
        return true;
    }
#endif

    return false;
}

void HqlCppTranslator::doBuildExprCount(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt)
{
    if (expr->hasProperty(keyedAtom))
        throwError(HQLERR_KeyedCountNonKeyable);

    IHqlExpression * dataset = expr->queryChild(0);
    CHqlBoundExpr temp;
    if (canBuildOptimizedCount(ctx, dataset, temp))
    {
        OwnedHqlExpr translated = temp.getTranslatedExpr();
        OwnedHqlExpr cast = ensureExprType(translated, expr->queryType());
        buildExpr(ctx, cast, tgt);
    }
    else
        doBuildExprAggregate(ctx, expr, tgt);
}

//---------------------------------------------------------------------------

IHqlExpression * HqlCppTranslator::queryOptimizedExists(BuildCtx & ctx, IHqlExpression * expr, IHqlExpression * dataset)
{
    node_operator dsOp = dataset->getOperator();
    //really this is isSimple()

    CHqlBoundExpr optimized;
    bool canOptimizeCount = canBuildOptimizedCount(ctx, dataset, optimized);
    node_operator op = (expr->getOperator() == no_exists) ? no_ne : no_eq;
    bool specialCase = false;
    switch (dsOp)
    {
    case no_select:
        specialCase = canOptimizeCount;
        break;
    default:
        specialCase = !canOptimizeCount && alwaysEvaluatesToBound(dataset);
        break;
    }

    if (specialCase)
    {
        CHqlBoundExpr temp;
        buildDataset(ctx, dataset, temp, FormatNatural);
        IHqlExpression * test;
        if (temp.count)
            test = LINK(temp.count);
        else
            test = getBoundSize(temp);
        return createBoolExpr(op, test, createConstant(test->queryType()->castFrom(false, 0)));
    }
    else if (canOptimizeCount)
    {
        IHqlExpression * count = optimized.expr;
        return createBoolExpr(op, LINK(count), createConstant(count->queryType()->castFrom(false, 0)));
    }
    return NULL;
}

void HqlCppTranslator::doBuildExprExists(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt)
{
    OwnedHqlExpr optimized = queryOptimizedExists(ctx, expr, expr->queryChild(0));
    if (optimized)
        tgt.expr.setown(optimized.getClear());
    else
        doBuildExprAggregate(ctx, expr, tgt);
}

//---------------------------------------------------------------------------

static IHqlExpression * createMinMax(node_operator compareOp, ITypeInfo * type, IHqlExpression * left, IHqlExpression * right)
{
    return createValue(no_if, LINK(type),
                            createBoolExpr(compareOp, LINK(left), LINK(right)), 
                            LINK(left), LINK(right));
}

bool HqlCppTranslator::doBuildAggregateMinMaxList(BuildCtx & ctx, const CHqlBoundTarget * target, IHqlExpression * expr, IHqlExpression * list, CHqlBoundExpr * tgt, node_operator compareOp)
{
    OwnedHqlExpr value;

    unsigned max = list->numChildren();
    switch(max)
    {
    case 0:
        value.setown(createNullExpr(expr));
        break;
    case 1:
        value.set(list->queryChild(0));
        break;
    case 2:
    case 3:
        {
            OwnedHqlExpr simple[3];
            for (unsigned i=0; i < max; i++)
            {
                CHqlBoundExpr bound;
                buildSimpleExpr(ctx, list->queryChild(i), bound);
                simple[i].setown(bound.getTranslatedExpr());
            }

            ITypeInfo * type = expr->queryType();
            if (max == 2)
                value.setown(createMinMax(compareOp, type, simple[0], simple[1]));
            else
            {
                OwnedHqlExpr cmp02 = createMinMax(compareOp, type, simple[0], simple[2]);
                OwnedHqlExpr cmp12 = createMinMax(compareOp, type, simple[1], simple[2]);
                value.setown(createValue(no_if, expr->getType(),
                            createBoolExpr(compareOp, LINK(simple[0]), LINK(simple[1])), 
                            LINK(cmp02), LINK(cmp12)));
            }
        }
    }

    if (value)
    {
        buildExprOrAssign(ctx, target, value, tgt);
        return true;
    }

    {
        CHqlBoundTarget temp;
        createTempFor(ctx, expr, temp);
        buildExprAssign(ctx, temp, list->queryChild(0));
        OwnedHqlExpr best = temp.getTranslatedExpr();
        for (unsigned i=1; i < list->numChildren(); i++)
        {
            CHqlBoundExpr bound;
            buildSimpleExpr(ctx, list->queryChild(i), bound);
            OwnedHqlExpr simple = bound.getTranslatedExpr();
            BuildCtx subctx(ctx);
            OwnedHqlExpr cond = createBoolExpr(compareOp, LINK(simple), LINK(best));
            buildFilter(subctx, cond);
            buildExprAssign(subctx, temp, simple);
        }
        buildExprOrAssign(ctx, target, best, tgt);
        return true;
    }
}

void HqlCppTranslator::doBuildAggregateList(BuildCtx & ctx, const CHqlBoundTarget * target, IHqlExpression * expr, CHqlBoundExpr * tgt)
{
    OwnedHqlExpr list = normalizeListCasts(expr->queryChild(0));

    if (list->getOperator() == no_alias_scope)
    {
        expandAliasScope(ctx, list);
        list.set(list->queryChild(0));
    }

    node_operator aggOp;
    switch (expr->getOperator())
    {
    case no_existslist:
        {
            //Fixed length lists should have been optimized away
            CHqlBoundExpr bound;
            buildExpr(ctx, list, bound);
            OwnedHqlExpr test;
            if (bound.count)
                test.set(bound.count);
            else
                test.setown(getBoundLength(bound));
            OwnedHqlExpr value = createValue(no_ne, makeBoolType(), LINK(test), ensureExprType(queryZero(), test->queryType()));
            OwnedHqlExpr translated = createTranslated(value);
            buildExprOrAssign(ctx, target, translated, tgt);
            return;
        }
    case no_countlist:
        {
            //Fixed length lists should have been optimized away
            CHqlBoundExpr bound;
            buildExpr(ctx, list, bound);
            OwnedHqlExpr test = getBoundCount(bound);
            OwnedHqlExpr value = ensureExprType(test, expr->queryType());
            OwnedHqlExpr translated = createTranslated(value);
            buildExprOrAssign(ctx, target, translated, tgt);
            return;
        }
    case no_sumlist:
        aggOp = no_sumgroup;
        if (list->getOperator() == no_list)
        {
            HqlExprArray args;
            ITypeInfo * exprType = expr->queryType();
            ForEachChild(i, list)
                args.append(*ensureExprType(list->queryChild(i), exprType));
            OwnedHqlExpr balanced = createBalanced(no_add, exprType, args);
            if (!balanced)
                balanced.setown(ensureExprType(queryZero(), exprType));
            buildExprOrAssign(ctx, target, balanced, tgt);
            return;
        }
        //special case fixed length lists
        break;
    case no_minlist:
        aggOp = no_mingroup;
        if (list->getOperator() == no_list)
        {
            if (doBuildAggregateMinMaxList(ctx, target, expr, list, tgt, no_lt))
                return;
        }
        break;
    case no_maxlist:
        aggOp = no_maxgroup;
        if (list->getOperator() == no_list)
        {
            if (doBuildAggregateMinMaxList(ctx, target, expr, list, tgt, no_gt))
                return;
        }
        break;
    default:
        throwUnexpectedOp(expr->getOperator());
    }

    ITypeInfo * elemType = list->queryType()->queryChildType();
    if (!elemType) elemType = defaultIntegralType;

    //Default implementation in terms of a dataset
    OwnedHqlExpr field = createField(valueAtom, LINK(elemType), NULL);
    OwnedHqlExpr record = createRecord(field);
    OwnedHqlExpr ds = createDataset(no_temptable, LINK(list), LINK(record));

    OwnedHqlExpr aggField = createField(valueAtom, expr->getType(), NULL);
    OwnedHqlExpr aggRecord = createRecord(aggField);
    OwnedHqlExpr self = createSelector(no_self, aggRecord, NULL);
    OwnedHqlExpr aggExpr = createValue(aggOp, expr->getType(), createSelectExpr(LINK(ds), LINK(field)));
    OwnedHqlExpr aggAssign = createAssign(createSelectExpr(LINK(self), LINK(aggField)), LINK(aggExpr));
    OwnedHqlExpr aggTransform = createValue(no_newtransform, makeTransformType(aggRecord->getType()), LINK(aggAssign));
    OwnedHqlExpr agg = createDataset(no_newaggregate, LINK(ds), createComma(LINK(aggRecord), LINK(aggTransform)));
    OwnedHqlExpr result = createNewSelectExpr(createRow(no_selectnth, LINK(agg), createConstantOne()), LINK(aggField));
    buildExprOrAssign(ctx, target, result, tgt);
}

//---------------------------------------------------------------------------

static HqlTransformerInfo graphIndependanceCheckerInfo("GraphIndependanceChecker");
class GraphIndependanceChecker : public NewHqlTransformer
{
public:
    GraphIndependanceChecker(IHqlExpression * _graph) : NewHqlTransformer(graphIndependanceCheckerInfo), graph(_graph) { independent = true; }

    void analyseExpr(IHqlExpression * expr)
    {
        if (!independent || alreadyVisited(expr))
            return;

        switch (expr->getOperator())
        {
        case no_getgraphresult:
        case no_getgraphloopresultset:
        case no_getgraphloopresult:
            if (expr->queryChild(1) == graph)
            {
                independent = false;
                return;
            }
            break;
        }
        NewHqlTransformer::analyseExpr(expr);
    }

    inline bool isIndependent() const { return independent; }

protected:
    LinkedHqlExpr graph;
    bool independent;
};


bool isGraphIndependent(IHqlExpression * expr, IHqlExpression * graph)
{
    switch (expr->getOperator())
    {
    case no_constant:
        return true;
    }
    GraphIndependanceChecker checker(graph);
    checker.analyse(expr, 0);
    return checker.isIndependent();
}

///--------------------------------------------------------------------------------------------------------------------

ChildGraphExprBuilder::ChildGraphExprBuilder(unsigned _numInputs)
: numInputs(_numInputs)
{
    numOutputs=0;
    represents.setown(createAttribute(graphAtom, createUniqueId()));
    resultsExpr.setown(createAttribute(resultsAtom, LINK(represents)));
}

IHqlExpression * ChildGraphExprBuilder::addDataset(IHqlExpression * expr)
{
    OwnedHqlExpr resultNumExpr;
    ForEachItemIn(i, results)
    {
        IHqlExpression & curSetResult = results.item(i);
        if (expr->queryBody() == curSetResult.queryChild(0)->queryBody())
        {
            resultNumExpr.set(curSetResult.queryChild(2));
            break;
        }
    }

    if (!resultNumExpr)
    {
        resultNumExpr.setown(getSizetConstant(numResults()));
        results.append(*createValue(no_setgraphresult, makeVoidType(), LINK(expr), LINK(represents), LINK(resultNumExpr)));
        numOutputs++;
    }

    HqlExprArray args;
    args.append(*LINK(expr->queryRecord()));
    args.append(*LINK(represents));
    args.append(*LINK(resultNumExpr));
    if (isGrouped(expr))
        args.append(*createAttribute(groupedAtom));
    if (!expr->isDataset())
        args.append(*createAttribute(rowAtom));
    args.append(*createAttribute(externalAtom, LINK(resultsExpr)));
    args.append(*createAttribute(_original_Atom, LINK(expr)));
    OwnedHqlExpr ret = createDataset(no_getgraphresult, args);
    if (expr->isDatarow())
        ret.setown(createRow(no_selectnth, LINK(ret), createComma(getSizetConstant(1), createAttribute(noBoundCheckAtom))));
    return ret.getClear();
}

void ChildGraphExprBuilder::addAction(IHqlExpression * expr)
{
    results.append(*LINK(expr));
}

unsigned ChildGraphExprBuilder::addInput()
{
    unsigned id = numResults();
    numInputs++;
    return id;
}

IHqlExpression * ChildGraphExprBuilder::getGraph()
{
    HqlExprArray args;
    args.append(*LINK(represents));
    args.append(*getSizetConstant(numResults()));
    args.append(*createActionList(results));
    return createValue(no_childquery, makeVoidType(), args);
}

//---------------------------------------------------------------------------
// Child dataset processing

ChildGraphBuilder::ChildGraphBuilder(HqlCppTranslator & _translator, IHqlExpression * subgraph)
: translator(_translator)
{
    represents.set(subgraph->queryChild(0));
    id = translator.nextActivityId();

    appendUniqueId(instanceName.append("child"), id);
    instanceExpr.setown(createQuoted(instanceName, makeBoolType()));
    resultsExpr.setown(createAttribute(resultsAtom, LINK(represents)));

    StringBuffer s;
    resultInstanceExpr.setown(createQuoted(appendUniqueId(s.append("res"), id), makeBoolType()));
    numResults = (unsigned)getIntValue(subgraph->queryChild(1));

    IHqlExpression * actions = subgraph->queryChild(2);
    actions->unwindList(results, no_actionlist);
}

void ChildGraphBuilder::generateGraph(BuildCtx & ctx)
{
    BuildCtx graphctx(ctx);

    //Make sure at least one results - because currently that's how we determine if new resourcing is being used
    //Remove this line once all engines use the new child queries exclusively
    if (numResults == 0) numResults++;

    OwnedHqlExpr query = createActionList(results);
    OwnedHqlExpr resourced = translator.getResourcedChildGraph(graphctx, query, represents, numResults, no_none);

    Owned<ParentExtract> extractBuilder = translator.createExtractBuilder(graphctx, PETchild, represents, resourced, true);
    if (!translator.queryOptions().serializeRowsetInExtract)
        extractBuilder->setAllowDestructor();
    translator.beginExtract(graphctx, extractBuilder);

    translator.doBuildThorSubGraph(graphctx, resourced, SubGraphChild, id, represents);

    EvalContext * instance = translator.queryEvalContext(graphctx);
    OwnedHqlExpr retInstanceExpr;
    if (instance && !translator.insideOnCreate(graphctx))
        retInstanceExpr.setown(instance->createGraphLookup(id, true));
    else
        retInstanceExpr.setown(translator.doCreateGraphLookup(graphctx, graphctx, id, "this", true));
    assertex(retInstanceExpr == instanceExpr);

    CHqlBoundExpr boundExtract;
    extractBuilder->endCreateExtract(boundExtract);

    HqlExprArray args;
    args.append(*LINK(instanceExpr));
    args.append(*createTranslated(boundExtract.length));
    args.append(*boundExtract.getTranslatedExpr());

    OwnedHqlExpr call = translator.bindFunctionCall(evaluateChildQueryInstanceAtom, args);
    CHqlBoundExpr bound;
    translator.buildExpr(graphctx, call, bound);
    StringBuffer s;
    s.append("Owned<IEclGraphResults> ");
    translator.generateExprCpp(s, resultInstanceExpr);
    s.append(" = ");
    translator.generateExprCpp(s, bound.expr);
    s.append(";");
    graphctx.addQuoted(s);

    translator.endExtract(graphctx, extractBuilder);
    ctx.associateExpr(resultsExpr, resultInstanceExpr);
}

void ChildGraphBuilder::generatePrefetchGraph(BuildCtx & _ctx, OwnedHqlExpr * retGraphExpr)
{
    BuildCtx ctx(_ctx);
    ctx.addGroup();

    BuildCtx aliasctx(ctx);
    aliasctx.addGroup();

    OwnedHqlExpr query = createActionList(results);
    OwnedHqlExpr resourced = translator.getResourcedChildGraph(ctx, query, represents, numResults, no_none);

    Owned<ParentExtract> extractBuilder = translator.createExtractBuilder(ctx, PETchild, represents, resourced, false);
    createBuilderAlias(aliasctx, extractBuilder);
    translator.beginExtract(ctx, extractBuilder);

    translator.doBuildThorSubGraph(ctx, resourced, SubGraphChild, id, represents);

    EvalContext * instance = translator.queryEvalContext(ctx);
    OwnedHqlExpr retInstanceExpr;
    assertex(instance && !translator.insideOnCreate(ctx));
    retInstanceExpr.setown(instance->createGraphLookup(id, true));
    assertex(retInstanceExpr == instanceExpr);

    retGraphExpr->setown(retInstanceExpr.getClear());
}

void ChildGraphBuilder::createBuilderAlias(BuildCtx & ctx, ParentExtract * extractBuilder)
{
    StringBuffer s;
    s.append("rtlRowBuilder & ");
    translator.generateExprCpp(s, extractBuilder->queryExtractName());
    s.append(" = builder;");
    ctx.addQuoted(s);
}

unique_id_t ChildGraphBuilder::buildLoopBody(BuildCtx & ctx, bool multiInstance)
{
    BuildCtx subctx(ctx);
    subctx.addGroup();

    OwnedHqlExpr query = createActionList(results);
    OwnedHqlExpr resourced = translator.getResourcedChildGraph(ctx, query, represents, numResults, no_loop);
    //Add a flag to indicate multi instance
    if (multiInstance)
        resourced.setown(appendOwnedOperand(resourced, createAttribute(multiInstanceAtom)));

    bool isGlobalThorLoop = translator.targetThor() && !translator.insideChildQuery(ctx);
    Owned<ParentExtract> extractBuilder = isGlobalThorLoop ? translator.createExtractBuilder(ctx, PETloop, represents, GraphRemote, false)
                                                           : translator.createExtractBuilder(ctx, PETloop, represents, resourced, false);

    createBuilderAlias(subctx, extractBuilder);

    translator.beginExtract(ctx, extractBuilder);
    translator.doBuildThorSubGraph(ctx, resourced, SubGraphChild, id, represents);
    translator.endExtract(ctx, extractBuilder);

    return id;
}



static HqlTransformerInfo graphLoopReplacerInfo("GraphLoopReplacer");
class GraphLoopReplacer : public NewHqlTransformer
{
public:
    GraphLoopReplacer(IHqlExpression * _rowsid, IHqlExpression * _represents, IHqlExpression * _counter, bool _isParallel) :
        NewHqlTransformer(graphLoopReplacerInfo), rowsid(_rowsid), represents(_represents), counter(_counter), isParallel(_isParallel)
    {
    }

    virtual IHqlExpression * createTransformed(IHqlExpression * expr)
    {
        switch (expr->getOperator())
        {
        case no_counter:
            if (expr->queryBody() == counter)
            {
                if (isParallel)
                {
                    HqlExprArray args;
                    args.append(*LINK(represents));
//                  unwindChildren(args, expr);
                    OwnedHqlExpr ret = createValue(no_loopcounter, expr->getType(), args);
                    //Yuk:  Wrap this in an alias to ensure it is evaluated at the correct place.
                    //there has to be a better way.....  We could...
                    //a) strictly defined when it can be evaluated - e.g., ctx->defines(graph) && (!parentctx || !parentctx->definesGraph)
                    //b) set a flag in the expression to indicate forced evaluation (even worse than the alias)
                    //c) add the code to evaluate no_loopcounter inside evaluateInContext
                    return createAlias(ret, internalAttrExpr);
                }
                else
                {
                    counterResult.setown(createCounterAsResult(counter, represents, 0));
                    return LINK(counterResult);
                }
            }
            break;
        case no_rowsetindex:
            {
                IHqlExpression * rowset = expr->queryChild(0);
                if (rowset->getOperator() != no_rowset)
                    break;
                IHqlExpression * rows = rowset->queryChild(0);
                if (rows->queryChild(1) != rowsid)
                    break;
                HqlExprArray args;
                args.append(*LINK(rows->queryChild(0)->queryRecord()));
                args.append(*LINK(represents));
                args.append(*transform(expr->queryChild(1)));
                return createDataset(no_getgraphloopresult, args);
            }
        case no_rowset:
            {
                IHqlExpression * rows = expr->queryChild(0);
                if (rows->queryChild(1) != rowsid)
                    break;
                HqlExprArray args;
                args.append(*LINK(rows->queryChild(0)->queryRecord()));
                args.append(*LINK(represents));
                return createValue(no_getgraphloopresultset, expr->getType(), args);
            }
        }
        return NewHqlTransformer::createTransformed(expr);
    }

    inline IHqlExpression * queryCounterResult() { return counterResult; }

protected:
    IHqlExpression * rowsid;
    IHqlExpression * represents;
    IHqlExpression * counter;
    OwnedHqlExpr counterResult;
    bool isParallel;
};



unique_id_t ChildGraphBuilder::buildGraphLoopBody(BuildCtx & ctx, bool isParallel)
{
    BuildCtx subctx(ctx);
    subctx.addGroup();

    OwnedHqlExpr query = createActionList(results);
    translator.traceExpression("Before Loop resource", query);
    OwnedHqlExpr resourced = translator.getResourcedChildGraph(ctx, query, represents, numResults, no_loop);
    translator.traceExpression("After Loop resource", resourced);

    //Add a flag to indicate multi instance
    if (isParallel)
    {
        HqlExprArray args;
        unwindChildren(args, resourced);
        args.append(*createAttribute(multiInstanceAtom));
        args.append(*createAttribute(delayedAtom));
        resourced.setown(resourced->clone(args));
    }

    bool isGlobalThorLoop = translator.targetThor() && !translator.insideChildQuery(ctx);
    Owned<ParentExtract> extractBuilder = isGlobalThorLoop ? translator.createExtractBuilder(ctx, PETloop, represents, GraphRemote, false)
                                                           : translator.createExtractBuilder(ctx, PETloop, represents, resourced, false);

    createBuilderAlias(subctx, extractBuilder);

    translator.beginExtract(ctx, extractBuilder);
    translator.doBuildThorSubGraph(ctx, resourced, SubGraphChild, id, represents);
    translator.endExtract(ctx, extractBuilder);

    return id;
}

unique_id_t ChildGraphBuilder::buildRemoteGraph(BuildCtx & ctx)
{
    BuildCtx subctx(ctx);
    subctx.addGroup();

    OwnedHqlExpr query = createActionList(results);
    OwnedHqlExpr resourced = translator.getResourcedChildGraph(ctx, query, represents, numResults, no_allnodes);

    Owned<ParentExtract> extractBuilder = translator.createExtractBuilder(ctx, PETremote, represents, GraphRemote, false);

    createBuilderAlias(subctx, extractBuilder);

    translator.beginExtract(ctx, extractBuilder);
    translator.doBuildThorSubGraph(ctx, resourced, SubGraphChild, id, represents);
    translator.endExtract(ctx, extractBuilder);

    return id;
}


void HqlCppTranslator::buildChildGraph(BuildCtx & ctx, IHqlExpression * expr)
{
    IHqlExpression * represents= expr->queryChild(0);
    OwnedHqlExpr resultsExpr = createAttribute(resultsAtom, LINK(represents));
    //Shouldn't really happen, but if this graph has already benn called just use the results
    if (ctx.queryMatchExpr(resultsExpr))
        return;

    ChildGraphBuilder graphBuilder(*this, expr);
    graphBuilder.generateGraph(ctx);
}

void HqlCppTranslator::beginExtract(BuildCtx & ctx, ParentExtract * extractBuilder)
{
    ctx.associate(*extractBuilder);
}

void HqlCppTranslator::endExtract(BuildCtx & ctx, ParentExtract * extractBuilder)
{ 
    extractBuilder->endUseExtract(ctx);
    ctx.removeAssociation(extractBuilder);
}

void HqlCppTranslator::buildAssignChildDataset(BuildCtx & ctx, const CHqlBoundTarget & target, IHqlExpression * expr)
{
    switch (expr->getOperator())
    {
    case no_call:
    case no_externalcall:
    case no_libraryinput:
        buildDatasetAssign(ctx, target, expr);
        return;
    }

    OwnedHqlExpr call;
    {
        ChildGraphExprBuilder builder(0);
        call.setown(builder.addDataset(expr));

        OwnedHqlExpr subquery = builder.getGraph();
        buildStmt(ctx, subquery);
    }

    buildExprAssign(ctx, target, call);
}


IHqlExpression * HqlCppTranslator::getResourcedChildGraph(BuildCtx & ctx, IHqlExpression * expr, IHqlExpression * graphIdExpr, unsigned numResults, node_operator graphKind)
{
    if (options.paranoidCheckNormalized || options.paranoidCheckDependencies)
        DBGLOG("Before resourcing a child graph");

    LinkedHqlExpr resourced = expr;
    checkNormalized(ctx, resourced);

    unsigned csfFlags = CSFindex|options.optimizeDiskFlag;
    switch (targetClusterType)
    {
    case HThorCluster:
        csfFlags |= CSFcompoundSpill;
        break;
    case ThorCluster:
    case ThorLCRCluster:
        //Don't compound spills inside a child query because it can cause non remote projects to become remote
        //And we'll also probably be using the roxie code to implement
        break;
    case RoxieCluster:
        break;
    }

    {
        unsigned time = msTick();
        CompoundSourceTransformer transformer(*this, CSFpreload|csfFlags);
        resourced.setown(transformer.process(resourced));
        checkNormalized(ctx, resourced);
        DEBUG_TIMER("EclServer: tree transform: optimize disk read", msTick()-time);
    }

    if (options.optimizeChildGraph)
    {
        unsigned time = msTick();
        traceExpression("BeforeOptimizeSub", resourced);
        resourced.setown(optimizeHqlExpression(resourced, getOptimizeFlags()|HOOcompoundproject));
        traceExpression("AfterOptimizeSub", resourced);
        DEBUG_TIMER("EclServer: optimize graph", msTick()-time);
    }

    traceExpression("BeforeResourcing Child", resourced);
    cycle_t time = msTick();
    HqlExprCopyArray activeRows;
    gatherActiveCursors(ctx, activeRows);
    if (graphKind == no_loop)
    {
        bool insideChild = insideChildQuery(ctx);
        resourced.setown(resourceLoopGraph(*this, activeRows, resourced, targetClusterType, graphIdExpr, &numResults, insideChild));
    }
    else
        resourced.setown(resourceNewChildGraph(*this, activeRows, resourced, targetClusterType, graphIdExpr, &numResults));

    DEBUG_TIMER("EclServer: resource graph", msTick()-time);
    checkNormalized(ctx, resourced);
    traceExpression("AfterResourcing Child", resourced);
    
    //Convert queries on preloaded into compound activities - before resourcing so keyed gets done correctly
    // Second attempt to spot compound disk reads - this time of spill files.  Since resourcing has removed
    // any sharing we don't need to bother about sharing.
    {
        unsigned time = msTick();

        CompoundSourceTransformer transformer(*this, csfFlags);
        resourced.setown(transformer.process(resourced));
        DEBUG_TIMER("EclServer: tree transform: optimize disk read", msTick()-time);
    }

    //Now call the optimizer again - the main purpose is to move projects over limits and into compound index/disk reads
    if (options.optimizeChildGraph)
    {
        unsigned time = msTick();
        traceExpression("BeforeOptimize2", resourced);
        resourced.setown(optimizeHqlExpression(resourced, getOptimizeFlags()|HOOcompoundproject));
        traceExpression("AfterOptimize2", resourced);
        DEBUG_TIMER("EclServer: optimize graph", msTick()-time);
    }

    if (numResults == 0) numResults++;

    HqlExprArray children;
    resourced->unwindList(children, no_actionlist);
    children.append(*createAttribute(numResultsAtom, getSizetConstant(numResults)));
    children.append(*LINK(graphIdExpr));
    resourced.setown(createValue(no_subgraph, makeVoidType(), children));

    if (options.paranoidCheckNormalized || options.paranoidCheckDependencies)
        DBGLOG("After resourcing a child graph");

    return resourced.getClear();
}


void HqlCppTranslator::buildChildDataset(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt)
{
    if (expr->isPure() && ctx.getMatchExpr(expr, tgt))
        return;

    LoopInvariantHelper helper;
    BuildCtx bestctx(ctx);
    if (options.optimizeLoopInvariant)
        helper.getBestContext(bestctx, expr);

    CHqlBoundTarget temp;
    //MORE: Should have similar code to buildTempExpr()
    createTempFor(bestctx, expr, temp);
    buildAssignChildDataset(bestctx, temp, expr);
    tgt.setFromTarget(temp);

    if (expr->isPure())
        bestctx.associateExpr(expr, tgt);
}


unique_id_t HqlCppTranslator::buildGraphLoopSubgraph(BuildCtx & ctx, IHqlExpression * dataset, IHqlExpression * selSeq, IHqlExpression * rowsid, IHqlExpression * body, IHqlExpression * counter, bool multiInstance)
{
    ChildGraphExprBuilder graphBuilder(0);

    OwnedHqlExpr transformedBody;
    OwnedHqlExpr counterResult;
    IHqlExpression * graphid = graphBuilder.queryRepresents();
    {
        const bool isParallel = multiInstance;
        GraphLoopReplacer replacer(rowsid, graphid, counter, isParallel);
        transformedBody.setown(replacer.transformRoot(body));
        counterResult.set(replacer.queryCounterResult());
    }

    if (counterResult)
        graphBuilder.addInput();

    OwnedHqlExpr result = createValue(no_setgraphloopresult, makeVoidType(), LINK(transformedBody), LINK(graphid));
    graphBuilder.addAction(result);
    OwnedHqlExpr subquery = graphBuilder.getGraph();

    ChildGraphBuilder builder(*this, subquery);
    return builder.buildGraphLoopBody(ctx, multiInstance);
}

unique_id_t HqlCppTranslator::buildRemoteSubgraph(BuildCtx & ctx, IHqlExpression * dataset)
{
    ChildGraphExprBuilder graphBuilder(0);
    if (dataset->isAction())
    {
        graphBuilder.addAction(dataset);
    }
    else
    {
        OwnedHqlExpr ignoredResult = graphBuilder.addDataset(dataset);
    }

    OwnedHqlExpr subquery = graphBuilder.getGraph();
    ChildGraphBuilder builder(*this, subquery);
    return builder.buildRemoteGraph(ctx);
}

//---------------------------------------------------------------------------
// Functions to check whether a dataset can be evaluated inline or not.

//MORE: These should probably be split out into an hqlinline.cpp

bool HqlCppTranslator::canIterateInline(BuildCtx * ctx, IHqlExpression * expr)
{
    return (isInlineOk() && ::canIterateInline(ctx, expr));
}

bool HqlCppTranslator::canAssignInline(BuildCtx * ctx, IHqlExpression * expr)
{
    if (!isInlineOk())
        return false;
    return options.allowInlineSpill ? ::canProcessInline(ctx, expr) : ::canAssignInline(ctx, expr);
}

bool HqlCppTranslator::canEvaluateInline(BuildCtx * ctx, IHqlExpression * expr)
{
    if (!isInlineOk())
        return false;
    return options.allowInlineSpill ? ::canProcessInline(ctx, expr) : ::canEvaluateInline(ctx, expr);
}

bool HqlCppTranslator::canProcessInline(BuildCtx * ctx, IHqlExpression * expr)
{
    if (!isInlineOk())
        return false;
    return ::canProcessInline(ctx, expr);
}

bool HqlCppTranslator::isInlineOk()
{
    if (!activeGraphCtx)
        return true;
    return true;
}

IHqlExpression * HqlCppTranslator::buildSpillChildDataset(BuildCtx & ctx, IHqlExpression * expr)
{
    CHqlBoundExpr bound;
    buildChildDataset(ctx, expr, bound);
    return bound.getTranslatedExpr();
}

IHqlExpression * HqlCppTranslator::forceInlineAssignDataset(BuildCtx & ctx, IHqlExpression * expr)
{
    loop
    {
        CHqlBoundExpr bound;
        if (expr->isPure() && ctx.getMatchExpr(expr, bound))
            return bound.getTranslatedExpr();

        if (canProcessInline(&ctx, expr) || (expr->getOperator() == no_translated))
            return LINK(expr);

        switch (expr->getOperator())
        {
        case no_compound:
            buildStmt(ctx, expr->queryChild(0));
            expr = expr->queryChild(1);
            break;
        default:
            return buildSpillChildDataset(ctx, expr);
        }
    }
}

//---------------------------------------------------------------------------
// Dataset temp creation

IHqlExpression * createGetResultFromWorkunitDataset(IHqlExpression * expr)
{
    IHqlExpression * name = queryPropertyChild(expr, nameAtom, 0);
    if (name)
        name = createExprAttribute(namedAtom, LINK(name));
    assertex(expr->isDataset());
    return createDataset(no_getresult, LINK(expr->queryRecord()), createComma(LINK(expr->queryProperty(sequenceAtom)), name));
}

void HqlCppTranslator::buildAssignSerializedDataset(BuildCtx & ctx, const CHqlBoundTarget & target, IHqlExpression * expr)
{
    OwnedITypeInfo serializedType = getSerializedForm(expr->queryType());
    assertex(recordTypesMatch(target.queryType(), serializedType));

    HqlExprArray args;
    args.append(*createRowSerializer(ctx, expr->queryRecord(), serializerAtom));
    args.append(*LINK(expr));
    OwnedHqlExpr call = bindFunctionCall(rowset2DatasetXAtom, args);
    buildExprAssign(ctx, target, call);
}

void HqlCppTranslator::buildSerializedDataset(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt)
{
    CHqlBoundTarget target;
    OwnedITypeInfo serializedType = getSerializedForm(expr->queryType());
    createTempFor(ctx, serializedType, target, typemod_none, FormatBlockedDataset);
    buildAssignSerializedDataset(ctx, target, expr);
    tgt.setFromTarget(target);
}


void HqlCppTranslator::buildAssignLinkedDataset(BuildCtx & ctx, const CHqlBoundTarget & target, IHqlExpression * expr)
{
    OwnedITypeInfo serializedType = getSerializedForm(target.queryType());
    assertex(recordTypesMatch(serializedType, expr->queryType()));

    IHqlExpression * record = ::queryRecord(target.queryType());
    HqlExprArray args;
    args.append(*createRowSerializer(ctx, record, deserializerAtom));
    args.append(*LINK(expr));
    OwnedHqlExpr call = bindFunctionCall(isGrouped(expr) ? groupedDataset2RowsetXAtom : dataset2RowsetXAtom, args, target.queryType());
    buildExprAssign(ctx, target, call);
}

void HqlCppTranslator::buildLinkedDataset(BuildCtx & ctx, ITypeInfo * type, IHqlExpression * expr, CHqlBoundExpr & tgt)
{
    CHqlBoundTarget target;
    createTempFor(ctx, type, target, typemod_none, FormatLinkedDataset);

    if (hasLinkedRow(expr->queryType()))
        buildDatasetAssign(ctx, target, expr);
    else
        buildAssignLinkedDataset(ctx, target, expr);

    tgt.setFromTarget(target);
}


void HqlCppTranslator::ensureDatasetFormat(BuildCtx & ctx, ITypeInfo * type, CHqlBoundExpr & tgt, ExpressionFormat format)
{
    switch (format)
    {
    case FormatBlockedDataset:
        if (isArrayRowset(tgt.queryType()))
        {
            OwnedHqlExpr deserializedExpr = tgt.getTranslatedExpr();
            LinkedHqlExpr savedCount = tgt.count;
            buildSerializedDataset(ctx, deserializedExpr, tgt);
            if (savedCount && !isFixedWidthDataset(deserializedExpr))
                tgt.count.set(savedCount);
            return;
        }
        break;
    case FormatLinkedDataset:
        if (!hasLinkCountedModifier(tgt.queryType()))
        {
            OwnedHqlExpr serializedExpr = tgt.getTranslatedExpr();
            buildLinkedDataset(ctx, type, serializedExpr, tgt);
            return;
        }
        break;
    case FormatArrayDataset:
        if (!isArrayRowset(tgt.queryType()))
        {
            OwnedHqlExpr serializedExpr = tgt.getTranslatedExpr();
            buildLinkedDataset(ctx, type, serializedExpr, tgt);
            return;
        }
        break;
    }
}

void HqlCppTranslator::buildDataset(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt, ExpressionFormat format)
{
    doBuildDataset(ctx, expr, tgt, format);
    ensureDatasetFormat(ctx, expr->queryType(), tgt, format);
}


void HqlCppTranslator::doBuildDataset(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt, ExpressionFormat format)
{
    if (expr->isPure() && ctx.getMatchExpr(expr, tgt))
        return;

/*
    OwnedHqlExpr transformed = normalizeAnyDatasetAliases(expr);
    if (transformed && (transformed != expr))
    {
        doBuildDataset(ctx, transformed, tgt, format);
        ctx.associateExpr(expr, tgt);
        return;
    }
*/

    node_operator op = expr->getOperator();
    switch (op)
    {
    case no_dataset_alias:
        if (!expr->hasProperty(_normalized_Atom))
        {
            OwnedHqlExpr uniqueChild = normalizeDatasetAlias(expr);
            doBuildDataset(ctx, uniqueChild, tgt, format);
        }
        else
            doBuildDataset(ctx, expr->queryChild(0), tgt, format);
        return;
    case no_alias:
        doBuildExprAlias(ctx, expr, &tgt);
        return;
    case no_owned_ds:
        buildTempExpr(ctx, expr, tgt);
        return;
    case no_null:
        {
            tgt.count.setown(getSizetConstant(0));
            tgt.length.setown(getSizetConstant(0));
            IHqlExpression * record = expr->queryRecord();
            ITypeInfo * type = makeTableType(makeRowType(record->getType()), NULL, NULL, NULL);
            if ((format == FormatLinkedDataset) || (format == FormatArrayDataset))
                type = makeAttributeModifier(type, getLinkCountedAttr());
            tgt.expr.setown(createValue(no_nullptr, makeReferenceModifier(type)));
            return;
        }
    case no_translated:
        expandTranslated(expr, tgt);
        return;
    case no_select:
        {
            if (isMultiLevelDatasetSelector(expr, false))
                break;

            Owned<IReferenceSelector> selected = buildReference(ctx, expr);
            selected->get(ctx, tgt);
            return;
        }
    case no_libraryinput:
        if (!buildExprInCorrectContext(ctx, expr, tgt, false))
            throwUnexpected();
        return;
    case no_call:
    case no_externalcall:
        if (!hasStreamedModifier(expr->queryType()))
        {
            buildTempExpr(ctx, expr, tgt);
            return;
        }
        break;
    case no_newaggregate:
        if (canAssignInline(&ctx, expr))
        {
            Owned<BoundRow> tempRow = declareTempAnonRow(ctx, ctx, expr);

            Owned<BoundRow> rowBuilder = createRowBuilder(ctx, tempRow);
            Owned<IReferenceSelector> createdRef = createReferenceSelector(rowBuilder);

            BuildCtx subctx(ctx);
            subctx.addGroup();
            doBuildRowAssignAggregate(subctx, createdRef, expr);
            finalizeTempRow(ctx, tempRow, rowBuilder);

            convertBoundRowToDataset(ctx, tgt, tempRow, format);
            return;
        }
        break;
    case no_id2blob:
        doBuildExprIdToBlob(ctx, expr, tgt);
        return;
    case no_rows:
        {
            if (!buildExprInCorrectContext(ctx, expr, tgt, false))
                throwError(HQLERR_RowsUsedOutsideContext);
            return;
        }
    case no_limit:
        if (expr->hasProperty(skipAtom) || expr->hasProperty(onFailAtom))
            break;
        doBuildDatasetLimit(ctx, expr, tgt, format);
        return;
    case no_compound_childread:
    case no_compound_childnormalize:
    case no_compound_childaggregate:
    case no_compound_selectnew:
    case no_compound_inline:
    case no_distributed:
    case no_preservemeta:
    case no_sorted:
    case no_nofold:
    case no_nohoist:
    case no_section:
    case no_sectioninput:
        buildDataset(ctx, expr->queryChild(0), tgt, format);
        return;
    case no_forcegraph:
#ifdef _DEBUG
        throwUnexpected();
#endif
        buildDataset(ctx, expr->queryChild(0), tgt, format);
        return;
    case no_getgraphresult:
        doBuildExprGetGraphResult(ctx, expr, tgt, format);
        return;
    case no_getresult:
    case no_workunit_dataset:
        if (!isGrouped(expr))
        {
            doBuildExprGetResult(ctx, expr, tgt);
            return;
        }
        break;
    case no_skip:
        {
            buildStmt(ctx, expr);
            OwnedHqlExpr null = createNullExpr(expr);
            buildDataset(ctx, null, tgt, format);
            return;
        }
    case no_serialize:
        if (isDummySerializeDeserialize(expr))
            doBuildDataset(ctx, expr->queryChild(0)->queryChild(0), tgt, format);
        else
            buildSerializedDataset(ctx, expr->queryChild(0), tgt);
        return;
    case no_deserialize:
        if (isDummySerializeDeserialize(expr))
            doBuildDataset(ctx, expr->queryChild(0)->queryChild(0), tgt, format);
        else
            buildLinkedDataset(ctx, expr->queryType(), expr->queryChild(0), tgt);
        return;
    case no_datasetfromrow:
        {
            IHqlExpression * row = expr->queryChild(0);
            if (isAlwaysActiveRow(row) && (format == FormatNatural))
            {
                Owned<IReferenceSelector> selector = buildActiveRow(ctx, row);
                BuildCtx groupctx(ctx);
                groupctx.addGroup();
                BoundRow * bound = bindSelectorAsRootRow(groupctx, selector, row);
                convertBoundRowToDataset(groupctx, tgt, bound, format);
                tgt.count.setown(getSizetConstant(1));
                ctx.associateExpr(expr, tgt);
                return;
            }
            break;
        }
    case no_inlinetable:
        if (doBuildDatasetInlineTable(ctx, expr, tgt, format))
            return;
        break;
    case no_compound:
        {
            buildStmt(ctx, expr->queryChild(0));
            buildDataset(ctx, expr->queryChild(1), tgt, format);
            return;
        }
    }

    bool singleRow = hasSingleRow(expr);
    bool useTempRow = singleRow && canAssignInline(&ctx, expr) && (format != FormatLinkedDataset) && (format != FormatArrayDataset);
    //Conditional row assignment if variable length causes offset to be recalculated outside of the if()
    //if (useTempRow && (op == no_if) && isVariableSizeRecord(expr->queryRecord()))
    //  useTempRow = false;

    if (useTempRow)
    {
        Owned<BoundRow> tempRow = declareTempAnonRow(ctx, ctx, expr);

        Owned<BoundRow> rowBuilder = createRowBuilder(ctx, tempRow);
        Owned<IHqlCppDatasetBuilder> builder = createSingleRowTempDatasetBuilder(expr->queryRecord(), rowBuilder);
        builder->buildDeclare(ctx);

        buildDatasetAssign(ctx, builder, expr);

        //builder->buildFinish(ctx, tempTarget);
        finalizeTempRow(ctx, tempRow, rowBuilder);

        convertBoundRowToDataset(ctx, tgt, tempRow, format);
    }
    else
    {
        if (!canAssignInline(&ctx, expr))
        {
            CHqlBoundTarget tempTarget;
            createTempFor(ctx, expr->queryType(), tempTarget, typemod_none, format);
            buildDatasetAssign(ctx, tempTarget, expr);
            tgt.setFromTarget(tempTarget);
            //buildTempExpr(ctx, expr, tgt);            // can't use this because it causes recursion on no_selectnth
        }
        else
        {
            Owned<IHqlCppDatasetBuilder> builder;

            IHqlExpression * record = expr->queryRecord();
            OwnedHqlExpr serializedRecord = getSerializedForm(record);
            if (format == FormatNatural)
            {
                if (record != serializedRecord)
                    ensureContextAvailable(ctx);
                if (!ctx.queryMatchExpr(codeContextMarkerExpr))
                {
                    if (record != serializedRecord)
                        throwError(HQLERR_LinkedDatasetNoContext);
                    format = FormatBlockedDataset;
                }
                else if ((record == serializedRecord) && !options.tempDatasetsUseLinkedRows)
                {
                    format = FormatBlockedDataset;
                }
                else
                {
                    format = FormatLinkedDataset;
                }
            }
            else if (record != serializedRecord)
                format = FormatLinkedDataset;   // Have to serialize it later - otherwise it won't be compatible

            if (format == FormatLinkedDataset || format == FormatArrayDataset)
            {
                IHqlExpression * choosenLimit = NULL;
                if ((op == no_choosen) && !isChooseNAllLimit(expr->queryChild(1)) && !queryRealChild(expr, 2))
                {
                    choosenLimit = expr->queryChild(1);
                    expr = expr->queryChild(0);
                }

                //MORE: Extract limit and choosen and pass as parameters
                builder.setown(createLinkedDatasetBuilder(record, choosenLimit));
            }
            else if ((op == no_choosen) && !isChooseNAllLimit(expr->queryChild(1)) && !queryRealChild(expr, 2))
            {
                //Build a limited builder - it is likely to be just as efficient, and often much more e.g., choosen(a+b, n)
                builder.setown(createChoosenDatasetBuilder(serializedRecord, expr->queryChild(1)));
                expr = expr->queryChild(0);
            }
            else
                builder.setown(createBlockedDatasetBuilder(serializedRecord));

            builder->buildDeclare(ctx);

            buildDatasetAssign(ctx, builder, expr);

            builder->buildFinish(ctx, tgt);
        }
    }
    if (singleRow)
        tgt.count.setown(getSizetConstant(1));
    else if (op == no_inlinetable)
    {
        IHqlExpression * transforms = expr->queryChild(0);
        if (!transformListContainsSkip(transforms))
            tgt.count.setown(getSizetConstant(transforms->numChildren()));
    }

    ctx.associateExpr(expr, tgt);
}

//---------------------------------------------------------------------------
// Dataset assignment - to temp

void HqlCppTranslator::buildDatasetAssign(BuildCtx & ctx, const CHqlBoundTarget & target, IHqlExpression * expr)
{
    node_operator op = expr->getOperator();
    switch (op)
    {
    case no_call:
    case no_externalcall:
        if (!hasStreamedModifier(expr->queryType()))
        {
            doBuildCall(ctx, &target, expr, NULL);
            return;
        }
        break;
    case no_getgraphresult:
        doBuildAssignGetGraphResult(ctx, target, expr);
        return;
    case no_workunit_dataset:
    case no_getresult:
        buildExprAssign(ctx, target, expr);
        return;
    case no_null:
        {
            CHqlBoundExpr bound;
            buildDataset(ctx, expr, bound, isArrayRowset(expr->queryType()) ? FormatLinkedDataset : FormatBlockedDataset);
            OwnedHqlExpr translated = bound.getTranslatedExpr();
            if (target.count) ctx.addAssign(target.count, bound.count);
            if (target.length) ctx.addAssign(target.length, bound.length);
            ctx.addAssign(target.expr, bound.expr);
            return;
        }
    case no_inlinetable:
        {
            //This will typically generate a loop.  If few items then it is more efficient to expand the assigns/clones out.
            if (expr->queryChild(0)->numChildren() > INLINE_TABLE_EXPAND_LIMIT)
            {
                CHqlBoundExpr bound;
                if (doBuildDatasetInlineTable(ctx, expr, bound, FormatNatural))
                {
                    OwnedHqlExpr translated = bound.getTranslatedExpr();
                    buildDatasetAssign(ctx, target, translated);
                    return;
                }
            }
            break;
        }
    case no_alias:
        {
            CHqlBoundExpr bound;
            buildDataset(ctx, expr, bound, FormatNatural);
            OwnedHqlExpr translated = bound.getTranslatedExpr();
            buildDatasetAssign(ctx, target, translated);
            return;
        }
    case no_owned_ds:
        {
            ITypeInfo * targetType = target.queryType();
            if (hasLinkCountedModifier(targetType) && hasWrapperModifier(targetType))
            {
                CHqlBoundExpr bound;
                buildDataset(ctx, expr->queryChild(0), bound, FormatLinkedDataset);
                OwnedHqlExpr compound = createValue(no_complex, bound.expr->getType(), LINK(bound.count), LINK(bound.expr));
                ctx.addAssign(target.expr, compound);
                return;
            }
            break;
        }
    case no_compound:
        {
            buildStmt(ctx, expr->queryChild(0));
            buildDatasetAssign(ctx, target, expr->queryChild(1));
            return;
        }
    case no_compound_childread:
    case no_compound_childnormalize:
    case no_compound_childaggregate:
    case no_compound_selectnew:
    case no_compound_inline:
    case no_distributed:
    case no_preservemeta:
    case no_sorted:
    case no_nofold:
    case no_nohoist:
    case no_section:
    case no_sectioninput:
        buildDatasetAssign(ctx, target, expr->queryChild(0));
        return;
    case no_serialize:
        if (isDummySerializeDeserialize(expr))
            buildDatasetAssign(ctx, target, expr->queryChild(0)->queryChild(0));
        else
            buildAssignSerializedDataset(ctx, target, expr->queryChild(0));
        return;
    case no_deserialize:
        if (isDummySerializeDeserialize(expr))
            buildDatasetAssign(ctx, target, expr->queryChild(0)->queryChild(0));
        else
            buildAssignLinkedDataset(ctx, target, expr->queryChild(0));
        return;
    case no_select:
        {
            bool isNew;
            IHqlExpression * ds = querySelectorDataset(expr, isNew);
            if (!isNew || ds->isDatarow())
            {
                Owned<IReferenceSelector> selected = buildReference(ctx, expr);
                selected->assignTo(ctx, target);
                return;
            }
            break;
        }
    case no_typetransfer:
        {
            IHqlExpression * child = expr->queryChild(0);
            if (expr->isDataset() && child->isDataset())
            {
                //Special case no-op type transfers and assignment from a call returning unknown-type dataset
                if (!recordTypesMatch(expr, child) &&
                    !(child->getOperator() == no_externalcall && recordTypesMatch(child, queryNullRecord())))
                {
                    CHqlBoundExpr bound;
                    buildDataset(ctx, child, bound, FormatNatural);
                    ITypeInfo * newType = cloneModifiers(bound.expr->queryType(), expr->queryType());
                    bound.expr.setown(createValue(no_typetransfer, newType, LINK(bound.expr)));
                    OwnedHqlExpr translated = bound.getTranslatedExpr();
                    buildDatasetAssign(ctx, target, translated);
                }
                else
                    buildDatasetAssign(ctx, target, child);
                return;
            }
            break;
        }
    }

    if (!canAssignInline(&ctx, expr) && (op != no_translated))
    {
        buildAssignChildDataset(ctx, target, expr);
        return;
    }

    ITypeInfo * to = target.queryType();
    ITypeInfo * exprType = expr->queryType();
    bool targetOutOfLine = isArrayRowset(to);
    switch (op)
    {
    case no_limit:
        assertex(!expr->hasProperty(skipAtom) && !expr->hasProperty(onFailAtom));
        //Do the limit check as a post test.  
        //It means we may read more records than we need to, but the code is inline, and the code is generally much better.
        if (target.count)
        {
            buildDatasetAssign(ctx, target, expr->queryChild(0));
            CHqlBoundExpr bound;
            bound.setFromTarget(target);
            doBuildCheckDatasetLimit(ctx, expr, bound);
            return;
        }
        break;
    case no_translated:
        {
            bool sourceOutOfLine = isArrayRowset(exprType);
            if (sourceOutOfLine != targetOutOfLine)
            {
                OwnedITypeInfo serializedSourceType = getSerializedForm(exprType);
                OwnedITypeInfo serializedTargetType = getSerializedForm(to);
                if (queryUnqualifiedType(serializedSourceType) == queryUnqualifiedType(serializedTargetType))
                {
                    if (targetOutOfLine)
                    {
                        buildAssignLinkedDataset(ctx, target, expr);
                    }
                    else
                    {
                        buildAssignSerializedDataset(ctx, target, expr);
                    }
                    return;
                }
            }
            break;
        }
    }

    if (recordTypesMatch(to, exprType))
    {
        switch (op)
        {
        case no_rows:
            {
                CHqlBoundExpr bound;
                buildDataset(ctx, expr, bound, FormatLinkedDataset);
                OwnedHqlExpr translated = bound.getTranslatedExpr();
                buildDatasetAssign(ctx, target, translated);
                return;
            }
        case no_select:
            {
                bool isNew;
                IHqlExpression * ds = querySelectorDataset(expr, isNew);
                if (isNew && !ds->isDatarow())
                    break;
            }
            //fall through
        case no_translated:
        case no_null:
        case no_id2blob:
            {
                _ATOM func = NULL;
                if (!isArrayRowset(to))
                {
                    if (!isArrayRowset(exprType))
                        func = dataset2DatasetXAtom;
                }
                else if (hasLinkCountedModifier(to))
                {
                    if (hasLinkCountedModifier(exprType))
                    {
                        CHqlBoundExpr bound;
                        buildDataset(ctx, expr, bound, FormatLinkedDataset);
                        assertex(bound.count && bound.expr);

                        if (hasWrapperModifier(to))
                        {
                            //assigns to count and rows members
                            StringBuffer s;
                            generateExprCpp(s, target.expr);
                            s.append(".set(");
                            generateExprCpp(s, bound.count);
                            s.append(",");
                            generateExprCpp(s, bound.expr);
                            s.append(");");
                            ctx.addQuoted(s);
                        }
                        else
                        {
                            ctx.addAssign(target.count, bound.count);
                            HqlExprArray args;
                            args.append(*LINK(bound.expr));
                            OwnedHqlExpr call = bindTranslatedFunctionCall(linkRowsetAtom, args);
                            ctx.addAssign(target.expr, call);
                        }
                        return;
                    }
                }

                if (func)
                {
                    HqlExprArray args;
                    args.append(*LINK(expr));
                    OwnedHqlExpr call = bindFunctionCall(func, args);
                    buildExprAssign(ctx, target, call);
                    return;
                }
            }
        }
    }

    IHqlExpression * record = ::queryRecord(to);
    Owned<IHqlCppDatasetBuilder> builder;
    if (targetOutOfLine)
    {
        IHqlExpression * choosenLimit = NULL;
        if ((op == no_choosen) && !isChooseNAllLimit(expr->queryChild(1)) && !queryRealChild(expr, 2))
        {
            choosenLimit = expr->queryChild(1);
            expr = expr->queryChild(0);
        }

        builder.setown(createLinkedDatasetBuilder(record, choosenLimit));
    }
    else
        builder.setown(createBlockedDatasetBuilder(record));
    builder->buildDeclare(ctx);

    buildDatasetAssign(ctx, builder, expr);

    builder->buildFinish(ctx, target);
}

//---------------------------------------------------------------------------

void HqlCppTranslator::doBuildCheckDatasetLimit(BuildCtx & ctx, IHqlExpression * expr, const CHqlBoundExpr & bound)
{
    IHqlExpression * record = expr->queryRecord();
    IHqlExpression * limit = expr->queryChild(1);

    OwnedHqlExpr test;
    if (!bound.count && bound.length && isFixedRecordSize(record))
    {
        OwnedHqlExpr size = bound.length->queryValue() ? LINK(bound.length) : createTranslated(bound.length);
        OwnedHqlExpr maxSize = createValue(no_mul, LINK(sizetType), ensureExprType(limit, sizetType), getSizetConstant(getFixedRecordSize(record)));
        test.setown(createBoolExpr(no_gt, ensureExprType(size, sizetType), LINK(maxSize)));
    }
    else
    {
        OwnedHqlExpr count = getBoundCount(bound);
        OwnedHqlExpr translatedCount = count->queryValue() ? LINK(count) : createTranslated(count);
        test.setown(createBoolExpr(no_gt, ensureExprType(translatedCount, sizetType), ensureExprType(limit, sizetType)));
    }
    OwnedHqlExpr folded = foldHqlExpression(test);
    LinkedHqlExpr fail = queryRealChild(expr, 2);

    if (folded->queryValue())
    {
        if (!folded->queryValue()->getBoolValue())
            return;

        StringBuffer failMessageText;
        if (fail)
        {
            OwnedHqlExpr failMessage = getFailMessage(fail, true);
            if (failMessage && failMessage->queryValue())
                failMessage->queryValue()->getStringValue(failMessageText);
        }
        if (failMessageText.length())
            WARNING1(HQLWRN_LimitAlwaysExceededX, failMessageText.str());
        else
            WARNING(HQLWRN_LimitAlwaysExceeded);
    }

    if (!fail)
        fail.setown(createFailAction("Limit exceeded", limit, NULL, queryCurrentActivityId(ctx)));

    BuildCtx subctx(ctx);
    buildFilter(subctx, folded);
    buildStmt(subctx, fail);
}

void HqlCppTranslator::doBuildDatasetLimit(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt, ExpressionFormat format)
{
    buildDataset(ctx, expr->queryChild(0), tgt, format);

    doBuildCheckDatasetLimit(ctx, expr, tgt);
}

bool HqlCppTranslator::doBuildDatasetInlineTable(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt, ExpressionFormat format)
{
    if (!options.generateStaticInlineTables)
        return false;

    IHqlExpression * transforms = expr->queryChild(0);
    IHqlExpression * record = expr->queryRecord();
    if (transforms->numChildren() == 0)
    {
        OwnedHqlExpr null = createDataset(no_null, LINK(record));
        buildDataset(ctx, null, tgt, format);
        return true;
    }

    BuildCtx declareCtx(*code, literalAtom);
    //Remove unique id when checking for constant datasets already generated
    OwnedHqlExpr exprNoUnique = removeProperty(expr, _uid_Atom);
    if (declareCtx.getMatchExpr(exprNoUnique, tgt))
        return true;

    HqlExprArray rows;
    unsigned maxRows = transforms->numChildren();
    unsigned row;
    for (row = 0; row < maxRows; row++)
    {
        OwnedHqlExpr constRow = createConstantRowExpr(transforms->queryChild(row));
        if (!constRow || !canGenerateStringInline(constRow->queryType()->getSize()))
            return false;
        rows.append(*constRow.getClear());
    }

    HqlExprArray boundRows;
    ForEachItemIn(i, rows)
    {
        CHqlBoundExpr bound;
        buildConstRow(record, &rows.item(i), bound);
        boundRows.append(*bound.expr.getClear());
    }

    Owned<ITypeInfo> rowType = makeConstantModifier(makeReferenceModifier(makeRowType(LINK(queryRecordType(expr->queryType())))));
    OwnedHqlExpr values = createValue(no_list, makeSetType(LINK(rowType)), boundRows);

    Owned<ITypeInfo> tableType = makeConstantModifier(makeArrayType(LINK(rowType), maxRows));
    OwnedITypeInfo rowsType = makeOutOfLineModifier(makeTableType(LINK(rowType), NULL, NULL, NULL));

    OwnedHqlExpr table = declareCtx.getTempDeclare(tableType, values);
    if (options.spanMultipleCpp)
    {
        BuildCtx protoctx(*code, mainprototypesAtom);
        protoctx.addDeclareExternal(table);
    }

    tgt.count.setown(getSizetConstant(maxRows));
    tgt.expr.setown(createValue(no_typetransfer, LINK(rowsType), LINK(table)));

    declareCtx.associateExpr(exprNoUnique, tgt);
    return true;
}


//---------------------------------------------------------------------------
// Dataset creation via builder

void HqlCppTranslator::buildDatasetAssignTempTable(BuildCtx & ctx, IHqlCppDatasetBuilder * target, IHqlExpression * expr)
{
    OwnedHqlExpr values = normalizeListCasts(expr->queryChild(0));
    if (values->getOperator() == no_null)
        return;

    IHqlExpression * record = expr->queryChild(1);
    OwnedHqlExpr rowsExpr;
    if (values->queryType()->getTypeCode() == type_set)
    {
        if ((values->getOperator() == no_list) && !values->isConstant())
        {
            ForEachChild(i, values)
            {
                BuildCtx loopctx(ctx);
                BoundRow * targetRow = target->buildCreateRow(loopctx);
                OwnedHqlExpr targetField = createSelectExpr(LINK(targetRow->querySelector()), LINK(record->queryChild(0)));
                buildAssign(loopctx, targetField, values->queryChild(i));
                target->finishRow(loopctx, targetRow);
            }
        }
        else
        {
            Owned<IHqlCppSetCursor> cursor = createSetSelector(ctx, values);
            BuildCtx loopctx(ctx);
            CHqlBoundExpr boundCurElement;
            cursor->buildIterateLoop(loopctx, boundCurElement, false);
            BoundRow * targetRow = target->buildCreateRow(loopctx);

            OwnedHqlExpr targetField = createSelectExpr(LINK(targetRow->querySelector()), LINK(record->queryChild(0)));
            OwnedHqlExpr value = boundCurElement.getTranslatedExpr();
            buildAssign(loopctx, targetField, value);
            target->finishRow(loopctx, targetRow);
        }
    }
    else
    {
        BuildCtx subctx(ctx);
        BoundRow * targetRow = target->buildCreateRow(subctx);
        Owned<IReferenceSelector> targetRef = buildActiveRow(subctx, targetRow->querySelector());
        buildRowAssign(subctx, targetRef, values);
        target->finishRow(subctx, targetRow);
    }
}

void HqlCppTranslator::buildDatasetAssignInlineTable(BuildCtx & ctx, IHqlCppDatasetBuilder * target, IHqlExpression * expr)
{
    IHqlExpression * transforms = expr->queryChild(0);
    if (transforms->numChildren() == 0)
        return;

    unsigned maxRows = transforms->numChildren();
    unsigned row;
    const bool copyConstantRows = true;//getFieldCount(expr->queryRecord()) > 2;
    for (row = 0; row < maxRows; row++)
    {
        IHqlExpression * transform = transforms->queryChild(row);
        OwnedHqlExpr rowValue = createRow(no_createrow, LINK(transform));

        BuildCtx subctx(ctx);
        CHqlBoundExpr bound;
        //Work in progress.  Check if there are several fields - otherwise not worth it.s
        if (doBuildRowConstantTransform(transform, bound))
        {
            BoundRow * row = bindConstantRow(subctx, rowValue, bound);
            if (target->buildLinkRow(subctx, row))
                continue;
        }

        BoundRow * targetRow = target->buildCreateRow(subctx);
        Owned<IReferenceSelector> targetRef = buildActiveRow(subctx, targetRow->querySelector());
        buildRowAssign(subctx, targetRef, rowValue);
        target->finishRow(subctx, targetRow);
    }
}


class InlineDatasetSkipCallback : public CInterface, implements IHqlCodeCallback
{
public:
    IMPLEMENT_IINTERFACE

    virtual void buildCode(HqlCppTranslator & translator, BuildCtx & ctx)
    {
        ctx.addContinue();
    }
};

void HqlCppTranslator::buildDatasetAssignProject(BuildCtx & ctx, IHqlCppDatasetBuilder * target, IHqlExpression * expr)
{
    BuildCtx iterctx(ctx);
    IHqlExpression * ds = expr->queryChild(0);
    IHqlExpression * counter = queryPropertyChild(expr, _countProject_Atom, 0);

    OwnedHqlExpr counterVar;
    if (counter)
    {
        counterVar.setown(iterctx.getTempDeclare(unsignedType, queryZero()));
    }

    bool containsSkip = transformContainsSkip(expr->queryChild(1));
    BoundRow * sourceCursor = buildDatasetIterate(iterctx, ds, containsSkip);
    if (counter)
    {
        iterctx.associateExpr(counter, counterVar);
        OwnedHqlExpr inc = createValue(no_postinc, LINK(unsignedType), LINK(counterVar));
        iterctx.addExpr(inc);
    }

    if (sourceCursor)
    {
        BoundRow * targetRow = target->buildCreateRow(iterctx);
        HqlExprAssociation * skipAssociation = NULL;
        if (containsSkip)
        {
            OwnedHqlExpr callback = createUnknown(no_unknown, makeVoidType(), NULL, new InlineDatasetSkipCallback);
            skipAssociation = ctx.associateExpr(skipActionMarker, callback);
        }

        Owned<IReferenceSelector> targetRef = buildActiveRow(iterctx, targetRow->querySelector());
        switch (expr->getOperator())
        {
        case no_hqlproject:
            doBuildRowAssignProject(iterctx, targetRef, expr);
            break;
        case no_newusertable:
            doBuildRowAssignUserTable(iterctx, targetRef, expr);
            break;
        }

        ctx.removeAssociation(skipAssociation);
        target->finishRow(iterctx, targetRow);
    }
}


void HqlCppTranslator::buildDatasetAssignJoin(BuildCtx & ctx, IHqlCppDatasetBuilder * target, IHqlExpression * expr)
{
    IHqlExpression * left = expr->queryChild(0);
    IHqlExpression * right = expr->queryChild(1);
    IHqlExpression * cond = expr->queryChild(2);

    IHqlExpression * selSeq = querySelSeq(expr);
    bool leftOuter = expr->hasProperty(leftonlyAtom) || expr->hasProperty(leftouterAtom);

    CHqlBoundExpr nullRhs;
    if (leftOuter)
        buildDefaultRow(ctx, right, nullRhs);

    BuildCtx leftIterCtx(ctx);
    BoundRow * leftCursor = buildDatasetIterate(leftIterCtx, left, false);
    bindTableCursor(leftIterCtx, left, leftCursor->queryBound(), no_left, selSeq);

    OwnedHqlExpr matchedAnyVar;
    if (leftOuter)
        matchedAnyVar.setown(leftIterCtx.getTempDeclare(queryBoolType(), queryBoolExpr(false)));

    BuildCtx rightIterCtx(leftIterCtx);
    BoundRow * rightCursor = buildDatasetIterate(rightIterCtx, right, false);
    bindTableCursor(rightIterCtx, right, rightCursor->queryBound(), no_right, selSeq);

    OwnedHqlExpr cseCond = options.spotCSE ? spotScalarCSE(cond) : LINK(cond);
    buildFilter(rightIterCtx, cseCond);
    if (!expr->hasProperty(leftonlyAtom))
    {
        BoundRow * targetRow = target->buildCreateRow(rightIterCtx);
        Owned<IReferenceSelector> targetRef = buildActiveRow(rightIterCtx, targetRow->querySelector());
        OwnedHqlExpr rowValue = createRow(no_createrow, LINK(expr->queryChild(3)));
        buildRowAssign(rightIterCtx, targetRef, rowValue);
        target->finishRow(rightIterCtx, targetRow);
    }
    if (matchedAnyVar)
    {
        buildAssignToTemp(rightIterCtx, matchedAnyVar, queryBoolExpr(true));

        OwnedHqlExpr test = getInverse(matchedAnyVar);
        leftIterCtx.addFilter(test);

        OwnedHqlExpr defaultRowPtr = getPointer(nullRhs.expr);
        bindTableCursor(leftIterCtx, right, defaultRowPtr, no_right, selSeq);

        BoundRow * targetRow = target->buildCreateRow(leftIterCtx);
        Owned<IReferenceSelector> targetRef = buildActiveRow(leftIterCtx, targetRow->querySelector());
        OwnedHqlExpr rowValue = createRow(no_createrow, LINK(expr->queryChild(3)));
        buildRowAssign(leftIterCtx, targetRef, rowValue);
        target->finishRow(leftIterCtx, targetRow);
    }
}


void HqlCppTranslator::buildDatasetAssignAggregate(BuildCtx & ctx, IHqlCppDatasetBuilder * target, IHqlExpression * expr)
{
    BuildCtx subctx(ctx);
    subctx.addGroup();
    BoundRow * targetRow = target->buildCreateRow(subctx);

    Owned<IReferenceSelector> targetRef = buildActiveRow(subctx, targetRow->querySelector());
    doBuildRowAssignAggregate(subctx, targetRef, expr);
    target->finishRow(subctx, targetRow);
}


void HqlCppTranslator::buildDatasetAssign(BuildCtx & ctx, IHqlCppDatasetBuilder * target, IHqlExpression * _expr)
{
    OwnedHqlExpr expr = forceInlineAssignDataset(ctx, _expr);

    bool isRowAssign = false;
    BuildCtx subctx(ctx);
    switch (expr->getOperator())
    {
    case no_addfiles:
        buildDatasetAssign(subctx, target, expr->queryChild(0));
        buildDatasetAssign(subctx, target, expr->queryChild(1));
        return;
    case no_temptable:
        buildDatasetAssignTempTable(subctx, target, expr);
        //MORE: Create rows and assign each one in turn.  Could possibly be done with a different dataset selector
        return;
    case no_inlinetable:
        buildDatasetAssignInlineTable(subctx, target, expr);
        return;
    case no_xmlproject:
        buildDatasetAssignXmlProject(subctx, target, expr);
        return;
    case no_datasetfromrow:
        {
            isRowAssign = true;
            expr.set(expr->queryChild(0));
            break;
        }
    case no_if:
        {
            CHqlBoundExpr bound;
            buildExpr(subctx, expr->queryChild(0), bound);
            IHqlStmt * filter = subctx.addFilter(bound.expr);
            buildDatasetAssign(subctx, target, expr->queryChild(1));

            IHqlExpression * elseExpr = expr->queryChild(2);
            if (elseExpr && elseExpr->getOperator() != no_null)
            {
                subctx.selectElse(filter);
                buildDatasetAssign(subctx, target, elseExpr);
            }
        }
        return;
    case no_null:
        return;
    case no_activetable:
    case no_temprow:
    case no_createrow:
    case no_projectrow:
    case no_typetransfer:
        isRowAssign = true;
        break;
    case no_newaggregate:
        buildDatasetAssignAggregate(subctx, target, expr);
        return;
    case no_hqlproject:
    case no_newusertable:
        buildDatasetAssignProject(subctx, target, expr);
        return;
    case no_compound_childread:
    case no_compound_childnormalize:
    case no_compound_childaggregate:
    case no_compound_selectnew:
    case no_compound_inline:
    case no_distributed:
    case no_preservemeta:
    case no_sorted:
    case no_nofold:
    case no_nohoist:
    case no_section:
    case no_sectioninput:
        buildDatasetAssign(subctx, target, expr->queryChild(0));
        return;
    case no_alias_scope:
//      expandAliasScope(subctx, expr);
        buildDatasetAssign(subctx, target, expr->queryChild(0));
        return;
    case no_filter:
        {
            //We want to evaluate invariant conditions outside of the loop, rather than inside the dataset assignment
            //Currently the test is whether the expression is independent of any tables.  Better would be to
            //see if the test was dependent on any of the datasets introduced by expr->queryChild(0).
            HqlExprArray conds;
            unwindFilterConditions(conds, expr);

            IHqlExpression * ds = expr->queryChild(0);
#if 0
            HqlExprCopyArray selectors;
            loop
            {
                selectors.append(*ds->queryNormalizedSelector());
                IHqlExpression * root = queryRoot(expr);
                if (!root || root->getOperator() != no_select)
                    break;
                bool isNew;
                ds = querySelectorDataset(root, isNew);
                if (!isNew)
                    break;
            }
#endif

            unsigned max = conds.ordinality();
            unsigned i = 0;
            bool optimized = false;
            while (i < max)
            {
                IHqlExpression & cur = conds.item(i);
#if 0
                bool overlap = false;
                ForEachItemIn(j, selectors)
                {
                    if (containsSelector(&cur, &selectors.item(j)))
                    {
                        overlap = true;
                        break;
                    }
                }
#else
                bool overlap = containsSelector(&cur, ds->queryNormalizedSelector());
#endif
                if (!overlap)
                {
                    buildFilter(subctx, &cur);
                    conds.remove(i);
                    optimized = true;
                    max--;
                }
                else
                    i++;
            }

            if (max == 0)
            {
                buildDatasetAssign(subctx, target, ds);
                return;
            }

            if (optimized)
            {
                conds.add(*LINK(ds), 0);
                expr.setown(expr->clone(conds));
            }
            break;
        }
    case no_join:
        buildDatasetAssignJoin(subctx, target, expr);
        return;
    }

    ITypeInfo * type = expr->queryType();
    if (type)
    {
        switch (type->getTypeCode())
        {
        case type_record:       // e.g. dataset.recordfield
        case type_row:
            isRowAssign = true;
            break;
        }
    }

    if (isRowAssign)
    {
        bool done = false;
        subctx.addGroup();

        //Some code primarily here to improve the generated code for productions inside parse statements for text parsing.
        //see if we can replace a memcpy of the child record with a link...
        if (!target->isRestricted())
        {
            switch (expr->getOperator())
            {
            case no_matchattr:
            case no_left:
            case no_right:
                {
                    //Only try for really simple cases...
                    Owned<IReferenceSelector> sourceRef = buildNewRow(subctx, expr);
                    Owned<BoundRow> sourceRow = sourceRef->getRow(subctx);
                    if (!target->buildLinkRow(subctx, sourceRow))
                    {
                        BoundRow * targetRow = target->buildCreateRow(subctx);
                        Owned<IReferenceSelector> targetRef = buildActiveRow(subctx, targetRow->querySelector());
                        buildRowAssign(subctx, targetRef, sourceRef);
                        target->finishRow(subctx, targetRow);
                    }
                    done = true;
                    break;
                }
            }
        }

        if (!done)
        {
            BoundRow * match = static_cast<BoundRow *>(ctx.queryAssociation(expr, AssocRow, NULL));
            if (match && target->buildLinkRow(subctx, match))
                done = true;
        }

        if (!done)
        {
            BoundRow * targetRow = target->buildCreateRow(subctx);
            Owned<IReferenceSelector> targetRef = buildActiveRow(subctx, targetRow->querySelector());
            buildRowAssign(subctx, targetRef, expr);
            target->finishRow(subctx, targetRow);
        }
    }
    else
    {
        if (!target->buildAppendRows(subctx, expr))
        {
            BoundRow * sourceRow = buildDatasetIterate(subctx, expr, false);
            if (sourceRow)
            {
                if (!target->buildLinkRow(subctx, sourceRow))
                {
                    BoundRow * targetRow = target->buildCreateRow(subctx);

                    Owned<IReferenceSelector> targetRef = buildActiveRow(subctx, targetRow->querySelector());
                    Owned<IReferenceSelector> sourceRef = buildActiveRow(subctx, sourceRow->querySelector());
                    buildRowAssign(subctx, targetRef, sourceRef);
                    target->finishRow(subctx, targetRow);
                }
            }
        }
    }
}

//---------------------------------------------------------------------------
// Dataset iteration

BoundRow * HqlCppTranslator::buildDatasetIterateSelectN(BuildCtx & ctx, IHqlExpression * expr, bool needToBreak)
{
    OwnedHqlExpr counter = ctx.getTempDeclare(sizetType, NULL);
    buildAssignToTemp(ctx, counter, expr->queryChild(1));
    BoundRow * cursor = buildDatasetIterate(ctx, expr->queryChild(0), needToBreak);
    if (cursor)
    {
        OwnedHqlExpr dec = createValue(no_predec, counter->getType(), LINK(counter));
        OwnedHqlExpr test = createBoolExpr(no_eq, LINK(dec), getSizetConstant(0));
        ctx.addFilter(test);
    }
    return cursor;
}


BoundRow * HqlCppTranslator::buildDatasetIterateChoosen(BuildCtx & ctx, IHqlExpression * expr, bool needToBreak)
{
    OwnedHqlExpr counter = ctx.getTempDeclare(sizetType, queryZero());

    CHqlBoundExpr boundLow, boundHigh;
    OwnedHqlExpr foldedHigh = foldHqlExpression(expr->queryChild(1));
    if (!isChooseNAllLimit(foldedHigh))
        buildSimpleExpr(ctx, foldedHigh, boundHigh);
    if (queryRealChild(expr, 2))
    {
        OwnedHqlExpr foldedLow = foldHqlExpression(expr->queryChild(2));
        OwnedHqlExpr low = adjustValue(foldedLow, -1);
        buildSimpleExpr(ctx, low, boundLow);
        if (boundHigh.expr)
            boundHigh.expr.setown(createValue(no_add, LINK(boundHigh.queryType()), LINK(boundHigh.expr), LINK(boundLow.expr)));
    }

    BoundRow * cursor = buildDatasetIterate(ctx, expr->queryChild(0), needToBreak);

    if (cursor)
    {
        OwnedHqlExpr inc = createValue(no_postinc, counter->getType(), LINK(counter));
        ctx.addExpr(inc);

        OwnedHqlExpr cond;
        if (boundLow.expr)
            extendConditionOwn(cond, no_and, createBoolExpr(no_gt, LINK(counter), LINK(boundLow.expr)));
        if (boundHigh.expr)
            extendConditionOwn(cond, no_and, createBoolExpr(no_le, LINK(counter), LINK(boundHigh.expr)));
        if (cond)
            ctx.addFilter(cond);
    }
    return cursor;
}


BoundRow * HqlCppTranslator::buildDatasetIterateLimit(BuildCtx & ctx, IHqlExpression * expr, bool needToBreak)
{
    OwnedHqlExpr counter = ctx.getTempDeclare(sizetType, queryZero());

    CHqlBoundExpr boundHigh;
    OwnedHqlExpr foldedHigh = foldHqlExpression(expr->queryChild(1));
    buildSimpleExpr(ctx, foldedHigh, boundHigh);

    BoundRow * cursor = buildDatasetIterate(ctx, expr->queryChild(0), needToBreak);
    if (cursor)
    {
        OwnedHqlExpr inc = createValue(no_preinc, counter->getType(), LINK(counter));
        OwnedHqlExpr cond = createBoolExpr(no_gt, LINK(inc), LINK(boundHigh.expr));
        BuildCtx subctx(ctx);
        subctx.addFilter(cond);

        LinkedHqlExpr fail = expr->queryChild(2);
        if (!fail || fail->isAttribute())
            fail.setown(createFailAction("Limit exceeded", foldedHigh, NULL, queryCurrentActivityId(ctx)));
        buildStmt(subctx, fail);
    }
    return cursor;
}


BoundRow * HqlCppTranslator::buildDatasetIterateProject(BuildCtx & ctx, IHqlExpression * expr, bool needToBreak)
{
    IHqlExpression * dataset = expr->queryChild(0);
    OwnedHqlExpr counterVar;
    IHqlExpression * counter = queryPropertyChild(expr, _countProject_Atom, 0);
    if (counter)
    {
        counterVar.setown(ctx.getTempDeclare(unsignedType, queryZero()));
    }

    bool containsSkip = transformContainsSkip(expr->queryChild(1));
    if (containsSkip)
        needToBreak = true;

    buildDatasetIterate(ctx, dataset, needToBreak);
    Owned<BoundRow> tempRow = declareTempAnonRow(ctx, ctx, expr);
    if (counter)
    {
        ctx.associateExpr(counter, counterVar);
        OwnedHqlExpr inc = createValue(no_postinc, LINK(unsignedType), LINK(counterVar));
        ctx.addExpr(inc);
    }

    Owned<BoundRow> rowBuilder = createRowBuilder(ctx, tempRow);

    OwnedHqlExpr leftSelect = createSelector(no_left, dataset, querySelSeq(expr));
    OwnedHqlExpr transform = replaceSelector(expr->queryChild(1), leftSelect, dataset->queryNormalizedSelector());

    HqlExprAssociation * skipAssociation = NULL;
    if (containsSkip)
    {
        OwnedHqlExpr callback = createUnknown(no_unknown, makeVoidType(), NULL, new InlineDatasetSkipCallback);
        skipAssociation = ctx.associateExpr(skipActionMarker, callback);
    }
    doTransform(ctx, transform, rowBuilder);

    ctx.removeAssociation(skipAssociation);     //remove it in case keeping hold of it causes issues.
    finalizeTempRow(ctx, tempRow, rowBuilder);

    return bindTableCursor(ctx, expr, tempRow->queryBound());
}


BoundRow * HqlCppTranslator::buildDatasetIterateUserTable(BuildCtx & ctx, IHqlExpression * expr, bool needToBreak)
{
    IHqlExpression * dataset = expr->queryChild(0);

    buildDatasetIterate(ctx, dataset, needToBreak);
    Owned<BoundRow> tempRow = declareTempAnonRow(ctx, ctx, expr);
    Owned<BoundRow> rowBuilder = createRowBuilder(ctx, tempRow);

    doTransform(ctx, expr->queryChild(2), rowBuilder);

    finalizeTempRow(ctx, tempRow, rowBuilder);

    return bindTableCursor(ctx, expr, tempRow->queryBound());
}


BoundRow * HqlCppTranslator::buildDatasetIterateSpecialTempTable(BuildCtx & ctx, IHqlExpression * expr, bool needToBreak)
{
    IHqlExpression * values = expr->queryChild(0);
    bool requiresTempRow = false;
    ITypeInfo * type = values->queryType()->queryChildType();
    switch (type->getTypeCode())
    {
    case type_alien:
    case type_bitfield:
        requiresTempRow = true;
        break;
    default:
        if (type->getSize() == UNKNOWN_LENGTH)
            requiresTempRow = true;
        break;
    }

    Owned<IHqlCppSetCursor> cursor = createSetSelector(ctx, values);
    CHqlBoundExpr boundCurElement;
    cursor->buildIterateLoop(ctx, boundCurElement, false);

    OwnedHqlExpr address = getPointer(boundCurElement.expr);
    if (requiresTempRow)
    {
        Owned<BoundRow> tempRow = declareTempAnonRow(ctx, ctx, expr);
        Owned<BoundRow> rowBuilder = createRowBuilder(ctx, tempRow);

        IHqlExpression * record = expr->queryRecord();
        OwnedHqlExpr target = createSelectExpr(LINK(rowBuilder->querySelector()), LINK(record->queryChild(0)));
        OwnedHqlExpr curValue = boundCurElement.getTranslatedExpr();
        buildAssign(ctx, target, curValue);
        finalizeTempRow(ctx, tempRow, rowBuilder);

        return bindTableCursor(ctx, expr, tempRow->queryBound());
    }
    else
    {
        assertex(!boundCurElement.length && !boundCurElement.count);
        address.setown(createValue(no_implicitcast, makeRowReferenceType(expr), LINK(address)));
        return bindTableCursor(ctx, expr, address);
    }
}


BoundRow * HqlCppTranslator::buildDatasetIterateStreamedCall(BuildCtx & ctx, IHqlExpression * expr, bool needToBreak)
{
    CHqlBoundExpr bound;
    doBuildExprCall(ctx, expr, bound);

    ITypeInfo * exprType = expr->queryType();
    Owned<ITypeInfo> wrappedType = makeWrapperModifier(LINK(exprType));
    OwnedHqlExpr temp = ctx.getTempDeclare(wrappedType, bound.expr);

    ctx.addLoop(NULL, NULL, false);

    Owned<ITypeInfo> wrappedRowType = makeWrapperModifier(LINK(queryRowType(exprType)));
    OwnedHqlExpr tempRow = ctx.getTempDeclare(wrappedRowType, NULL);

    StringBuffer s;
    generateExprCpp(s, tempRow).append(".setown(");
    generateExprCpp(s, temp).append("->nextRow());");
    ctx.addQuoted(s);

    s.clear().append("if (!");generateExprCpp(s, tempRow).append(".getbytes()) break;");
    ctx.addQuoted(s);
    return bindTableCursor(ctx, expr, tempRow);
}


BoundRow * HqlCppTranslator::buildDatasetIterate(BuildCtx & ctx, IHqlExpression * expr, bool needToBreak)
{
    if (!canProcessInline(&ctx, expr))
    {
        Owned<IHqlCppDatasetCursor> cursor = createDatasetSelector(ctx, expr);
        return cursor->buildIterateLoop(ctx, needToBreak);
    }

    switch (expr->getOperator())
    {
    case no_dataset_alias:
        if (!expr->hasProperty(_normalized_Atom))
        {
            OwnedHqlExpr uniqueChild = normalizeDatasetAlias(expr);
            BoundRow * childCursor = buildDatasetIterate(ctx, uniqueChild, needToBreak);
            return rebindTableCursor(ctx, expr, childCursor, no_none, NULL);
        }
        else
        {
            throwUnexpected();
            //The following would only be triggered for a splitter (not yet generated), and that would require
            //disambiguation when that was built.
            BoundRow * childCursor = buildDatasetIterate(ctx, expr->queryChild(0), needToBreak);
            return rebindTableCursor(ctx, expr, childCursor, no_none, NULL);
        }
    case no_null:
        buildFilter(ctx, queryBoolExpr(false));
        return NULL;
    case no_filter:
        {
            IHqlExpression * dataset = expr->queryChild(0);
#ifdef _OPTIMZE_INLINE_FILTERS_
            //Good code, but messes up accidental cse in some createSegmentMonitor calls.
            HqlExprAttr invariant;
            OwnedHqlExpr cond = extractFilterConditions(invariant, expr, dataset);
            if (invariant)
                buildFilter(ctx, invariant);

            //MORE: if (canAssignInline(ctx, ds) && !canIterateInline(ctx, ds)) break;
            BoundRow * cursor = buildDatasetIterate(ctx, dataset, needToBreak);
            if (cond)
                buildFilter(ctx, cond);
#else
            //MORE: if (canAssignInline(ctx, ds) && !canIterateInline(ctx, ds)) break;
            BoundRow * cursor = buildDatasetIterate(ctx, dataset, needToBreak);
            unsigned max = expr->numChildren();
            for (unsigned i=1; i < max; i++)
                buildFilter(ctx, expr->queryChild(i));
#endif
            return cursor;
        }
    case no_id2blob:
    case no_select:
    case no_translated:
        {
            Owned<IHqlCppDatasetCursor> cursor = createDatasetSelector(ctx, expr);
            return cursor->buildIterateLoop(ctx, needToBreak);
        }
    case no_choosen:
        return buildDatasetIterateChoosen(ctx, expr, needToBreak);
    case no_limit:
        return buildDatasetIterateLimit(ctx, expr, needToBreak);
    case no_index:
    case no_selectnth:
        return buildDatasetIterateSelectN(ctx, expr, needToBreak);
    case no_hqlproject:
        return buildDatasetIterateProject(ctx, expr, needToBreak);
    case no_newusertable:
        return buildDatasetIterateUserTable(ctx, expr, needToBreak);
    case no_compound_childread:
    case no_compound_childnormalize:
    case no_compound_childaggregate:
    case no_compound_selectnew:
    case no_compound_inline:
    case no_distributed:
    case no_preservemeta:
    case no_sorted:
    case no_nofold:
    case no_nohoist:
        return buildDatasetIterate(ctx, expr->queryChild(0), needToBreak);
    case no_sectioninput:
    case no_section:
        {
            BoundRow * row = buildDatasetIterate(ctx, expr->queryChild(0), needToBreak);
#ifdef _DEBUG
            StringBuffer s;
            if (expr->getOperator() == no_section)
                s.append("//---- section ");
            else
                s.append("//---- end section ");
            getStringValue(s, expr->queryChild(1), "<?>").append(" ");
            getStringValue(s, expr->queryChild(2)).append("----");
            ctx.addQuoted(s);
#endif
            return row;
        }
    case no_alias_scope:
//      expandAliasScope(ctx, expr);
        return buildDatasetIterate(ctx, expr->queryChild(0), needToBreak);
    case no_temptable:
        {
            IHqlExpression * values = expr->queryChild(0);
            if (values->queryType()->getTypeCode() == type_set)
            {
                if (values->getOperator() == no_alias)
                    values = values->queryChild(0);

                bool special = false;
                switch (values->getOperator())
                {
                case no_getresult:
                case no_null:
                    special = true;
                    break;
                }
                if (special)
                    return buildDatasetIterateSpecialTempTable(ctx, expr, needToBreak);
            }
            break;
        }
    case no_call:
    case no_externalcall:
        if (hasStreamedModifier(expr->queryType()))
            return buildDatasetIterateStreamedCall(ctx, expr, needToBreak);
        break;

#if 0
    //Following should improve the code, but I'm not sure how to correctly convert a referenceSelector to a boundExpr (since it may be with an existing row)
    case no_datasetfromrow:
        if (!needToBreak)
        {
            BoundRow * row = buildNewRow(ctx, expr->queryChild(0));
            bindTableCursor(ctx, expr, tempRow->queryBound(), no_none, NULL);
            return row;
        }
        break;
#endif

    }

    Owned<IHqlCppDatasetCursor> cursor = createDatasetSelector(ctx, expr);
    return cursor->buildIterateLoop(ctx, needToBreak);
}

//---------------------------------------------------------------------------
// Row Assignment

void HqlCppTranslator::buildCompoundAssign(BuildCtx & ctx, IHqlExpression * left, IReferenceSelector * leftSelector, IHqlExpression * rightScope, IHqlExpression * rightSelector)
{
    switch (left->getOperator())
    {
    case no_ifblock:
        {
            BuildCtx subctx(ctx);
            OwnedHqlExpr test = replaceSelector(left->queryChild(0), querySelfReference(), leftSelector->queryExpr());
            buildFilter(subctx, test);
            buildCompoundAssign(subctx, left->queryChild(1), leftSelector, rightScope, rightSelector);

            //This calculates the size of the previous block.  It means that subsequent uses of the 
            //offsets are cached - even if they are inside another ifblock().
            CHqlBoundExpr bound;
            IHqlExpression * mapexpr = createSelectExpr(LINK(leftSelector->queryExpr()), LINK(left));
            OwnedHqlExpr size = createValue(no_sizeof, makeIntType(4,false), mapexpr);
            buildCachedExpr(ctx, size, bound);
        }
        break;
    case no_field:
        {
            Owned<IReferenceSelector> selectedLeft = leftSelector->select(ctx, left);
            OwnedHqlExpr selectedRight;
            IHqlExpression * leftRecord = ::queryRecord(leftSelector->queryType());
            if (!rightScope || (leftRecord==rightScope))
            {
                selectedRight.setown(createSelectExpr(LINK(rightSelector), LINK(left)));
            }
            else
            {
                IHqlSimpleScope * scope = rightScope->querySimpleScope();
                IHqlExpression * resolved = scope->lookupSymbol(left->queryName());
                assertex(resolved);
                selectedRight.setown(createSelectExpr(LINK(rightSelector), resolved));
            }

            if (left->queryType()->getTypeCode() == type_row)
                buildCompoundAssign(ctx, left->queryRecord(), selectedLeft, selectedRight->queryRecord(), selectedRight);
            else
                selectedLeft->set(ctx, selectedRight);
            break;
        }
        break;
    case no_record:
        {
            ForEachChild(i, left)
                buildCompoundAssign(ctx, left->queryChild(i), leftSelector, rightScope, rightSelector);
            break;
        }
    case no_attr:
    case no_attr_expr:
    case no_attr_link:
        break;
    default:
        UNIMPLEMENTED;
    }
}


void HqlCppTranslator::buildCompoundAssign(BuildCtx & ctx, IHqlExpression * left, IHqlExpression * right)
{
    //MORE: May need to resolve lhs and rhs in scope to find out the record type.
//  buildCompoundAssign(ctx, column->queryRecord(), selector->queryExpr(), value->queryRecord(), value);
    UNIMPLEMENTED;
}


void HqlCppTranslator::doBuildRowAssignAggregateClear(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr)
{
    IHqlExpression * transform = expr->queryChild(2);

    unsigned numAggregates = transform->numChildren();
    unsigned idx;
    OwnedHqlExpr self = getSelf(expr);
    for (idx = 0; idx < numAggregates; idx++)
    {
        IHqlExpression * cur = transform->queryChild(idx);
        Owned<IReferenceSelector> curTarget = createSelfSelect(ctx, target, cur->queryChild(0), self);
        IHqlExpression * src = cur->queryChild(1);

        switch (src->getOperator())
        {
        case no_countgroup:
        case no_maxgroup:
        case no_mingroup:
        case no_sumgroup:
        case no_existsgroup:
            curTarget->buildClear(ctx, 0);
            break;
        default:
            if (src->isConstant())
                curTarget->set(ctx, src);
            else
                curTarget->buildClear(ctx, 0);
            break;
        }
    }
}


void HqlCppTranslator::doBuildRowAssignAggregateNext(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr, bool isSingleExists, IHqlExpression * alreadyDoneExpr)
{
    IHqlExpression * transform = expr->queryChild(2);

    unsigned numAggregates = transform->numChildren();
    OwnedHqlExpr self = getSelf(expr);
    OwnedHqlExpr notAlreadyDone = alreadyDoneExpr ? getInverse(alreadyDoneExpr) : NULL;
    bool isVariableOffset = false;
    for (unsigned idx = 0; idx < numAggregates; idx++)
    {
        IHqlExpression * cur = transform->queryChild(idx);
        if (cur->isAttribute())
            continue;

        IHqlExpression * targetSelect = cur->queryChild(0);
        Owned<IReferenceSelector> curTarget = createSelfSelect(ctx, target, targetSelect, self);
        IHqlExpression * src = cur->queryChild(1);
        IHqlExpression * arg = src->queryChild(0);
        IHqlExpression * cond = src->queryChild(1);

        BuildCtx condctx(ctx);
        node_operator srcOp = src->getOperator();
        switch (srcOp)
        {
        case no_countgroup:
            {
                assertex(!(arg && isVariableOffset));
                if (arg)
                    buildFilter(condctx, arg);
                OwnedHqlExpr one = getSizetConstant(1);
                if (isVariableOffset)
                {
                    IHqlStmt * ifStmt = condctx.addFilter(notAlreadyDone);
                    curTarget->set(condctx, one);
                    condctx.selectElse(ifStmt);
                }
                buildIncrementAssign(condctx, curTarget, one);
            }
            break;
        case no_sumgroup:
            {
                assertex(!(cond && isVariableOffset));
                if (cond)
                    buildFilter(condctx, cond);
                if (isVariableOffset)
                {
                    IHqlStmt * ifStmt = condctx.addFilter(notAlreadyDone);
                    curTarget->set(condctx, arg);
                    condctx.selectElse(ifStmt);
                }
                buildIncrementAssign(condctx, curTarget, arg);
            }
            break;
        case no_maxgroup:
        case no_mingroup:
            {
                node_operator op = (srcOp == no_maxgroup) ? no_gt : no_lt;
                assertex(!cond);
                OwnedHqlExpr castArg = ensureExprType(arg, targetSelect->queryType());      // cast to correct type, assume it can fit in the target type.
                OwnedHqlExpr temp = buildSimplifyExpr(condctx, castArg);
                OwnedHqlExpr compare = createBoolExpr (op, LINK(temp), LINK(curTarget->queryExpr()));
                if (notAlreadyDone)
                    compare.setown(createBoolExpr(no_or, LINK(notAlreadyDone), compare.getClear()));

                buildFilter(condctx, compare);
                curTarget->set(condctx, temp);
            }
            break;
        case no_existsgroup:
            assertex(!(arg && isVariableOffset));
            if (arg)
                buildFilter(condctx, arg);
            curTarget->set(condctx, queryBoolExpr(true));
            if (isSingleExists)
                condctx.addBreak();
            break;
        default:
            if (!src->isConstant() || isVariableOffset)
            {
                condctx.addFilter(notAlreadyDone);
                curTarget->set(condctx, src);
            }
            break;
        }
        if (targetSelect->queryType()->getSize() == UNKNOWN_LENGTH)
           isVariableOffset = true;
    }
    if (alreadyDoneExpr)
        buildAssignToTemp(ctx, alreadyDoneExpr, queryBoolExpr(true));
}


void HqlCppTranslator::doBuildRowAssignAggregate(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr)
{
    IHqlExpression * dataset = expr->queryChild(0);
    IHqlExpression * transform = expr->queryChild(2);
    unsigned numAggregates = transform->numChildren();

    if (isKeyedCountAggregate(expr))
        throwError(HQLERR_KeyedCountNonKeyable);

    bool needGuard = false;
    bool isSingleExists = true;
    unsigned idx;
    for (idx = 0; idx < numAggregates; idx++)
    {
        IHqlExpression * cur = transform->queryChild(idx);
        if (cur->isAttribute())
            continue;

        IHqlExpression * tgt = cur->queryChild(0);
        IHqlExpression * src = cur->queryChild(1);
        switch (src->getOperator())
        {
        case no_countgroup:
        case no_sumgroup:
            isSingleExists = false;
            break;
        case no_existsgroup:
            break;
        case no_mingroup:
            isSingleExists = false;
            needGuard = true;
            break;
        case no_maxgroup:
            isSingleExists = false;
            if (!isNullValueMinimumValue(src->queryType()))
                needGuard = true;
            break;
        default:
            isSingleExists = false;
            if (!src->isConstant())
                needGuard = true;
            break;
        }
        if ((tgt->queryType()->getSize() == UNKNOWN_LENGTH) && (idx+1 != numAggregates))
            needGuard = true;
    }

    OwnedHqlExpr guard;
    if (needGuard)
    {
        Owned<ITypeInfo> boolType = makeBoolType(); 
        guard.setown(ctx.getTempDeclare(boolType, queryBoolExpr(false)));
    }

    doBuildRowAssignAggregateClear(ctx, target, expr);
    BuildCtx condctx(ctx);
    BoundRow * cursor = buildDatasetIterate(condctx, dataset, isSingleExists);
    doBuildRowAssignAggregateNext(condctx, target, expr, isSingleExists, guard);
}

void HqlCppTranslator::doBuildRowAssignProject(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr)
{
    IHqlExpression * dataset = expr->queryChild(0);
    IHqlExpression * counter = queryPropertyChild(expr, _countProject_Atom, 0);
    if (counter && !ctx.queryMatchExpr(counter))
        throwError(HQLERR_CounterNotFound);

    BuildCtx subctx(ctx);

    assertex(target->isRoot());
    IHqlExpression * selSeq = querySelSeq(expr);
    OwnedHqlExpr leftSelect = createSelector(no_left, dataset, selSeq);
    OwnedHqlExpr activeDataset = ensureActiveRow(dataset->queryNormalizedSelector());
    OwnedHqlExpr transform = queryNewReplaceSelector(expr->queryChild(1), leftSelect, activeDataset);
    Owned<BoundRow> selfCursor;
    if (!transform)
    {
        subctx.addGroup();
        selfCursor.set(bindSelectorAsSelf(subctx, target, expr));
        //Mapping may potentially be ambiguous, so do things correctly (see hqlsource for details)
        BoundRow * prevCursor = resolveSelectorDataset(subctx, dataset->queryNormalizedSelector());
        transform.set(expr->queryChild(1));

        bindTableCursor(subctx, dataset, prevCursor->queryBound(), no_left, selSeq);
    }
    else
    {
        //Not introducing any new left rows => no problem assigning to target selector
        selfCursor.setown(target->getRow(subctx));
    }

    doTransform(subctx, transform, selfCursor);
}

void HqlCppTranslator::doBuildRowAssignCreateRow(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr)
{
    IHqlExpression * transform = expr->queryChild(0);
    if (transform->isConstant())
    {
#ifdef USE_CONSTANT_ROW_FOR_ASSIGN
        //Generally not worthwhile - unless maybe it has a large number of fields....
        CHqlBoundExpr bound;
        if (doBuildRowConstantTransform(transform, bound))
        {
            OwnedHqlExpr raw = bound.getTranslatedExpr();
            buildRowAssign(ctx, target, raw);
            return;
        }
#endif
    }

    Owned<BoundRow> selfCursor = target->getRow(ctx);
    doTransform(ctx, transform, selfCursor);
}
        
void HqlCppTranslator::doBuildRowAssignNullRow(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr)
{
    target->buildClear(ctx, 0);
}
        
void HqlCppTranslator::doBuildRowAssignProjectRow(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr)
{
    IHqlExpression * srcRow = expr->queryChild(0);
    IHqlExpression * transform = expr->queryChild(1);

    Owned<IReferenceSelector> source = buildNewRow(ctx, srcRow);
    BuildCtx subctx(ctx);

    OwnedHqlExpr leftSelect = createSelector(no_left, srcRow, querySelSeq(expr));
    OwnedHqlExpr newTransform = replaceSelector(transform, leftSelect, srcRow);

    Owned<BoundRow> selfCursor = target->getRow(subctx);
    doTransform(subctx, newTransform, selfCursor);
}
        
void HqlCppTranslator::doBuildRowAssignSerializeRow(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr)
{
    IHqlExpression * srcRow = expr->queryChild(0);

    Owned<IReferenceSelector> source = buildNewRow(ctx, srcRow);

    BuildCtx subctx(ctx);

    Owned<BoundRow> leftCursor = source->getRow(subctx);
    BoundRow * selfCursor = bindSelectorAsSelf(subctx, target, expr);
    IHqlExpression * unserializedRecord = srcRow->queryRecord();

    //If builder isn't provided then the target must be a fixed size record that doesn't require serialization
    //Therefore this should never be called.
    assertex(selfCursor->queryBuilder());
    {
        HqlExprArray args;
        args.append(*createRowSerializer(ctx, unserializedRecord, serializerAtom));
        args.append(*LINK(srcRow));

        Owned<ITypeInfo> type = makeTransformType(expr->queryRecord()->getType());
        OwnedHqlExpr call = bindFunctionCall(rtlSerializeToBuilderAtom, args, type);
        doTransform(subctx, call, selfCursor);
        //MORE: This doesn't associated the returned size with the target if assigned to a child field.
        //very unusual code, so not too concerned.
    }

    subctx.removeAssociation(selfCursor);
}
        
void HqlCppTranslator::doBuildRowAssignUserTable(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr)
{
    Owned<BoundRow> selfCursor = target->getRow(ctx);
    doTransform(ctx, expr->queryChild(2), selfCursor);
}


void HqlCppTranslator::buildRowAssign(BuildCtx & ctx, IReferenceSelector * target, IHqlExpression * expr)
{
    switch (expr->getOperator())
    {
    case no_temprow:
        throwUnexpected();
    case no_projectrow:
        doBuildRowAssignProjectRow(ctx, target, expr);
        return;
    case no_createrow:
        doBuildRowAssignCreateRow(ctx, target, expr);
        return;
    case no_null:
        doBuildRowAssignNullRow(ctx, target, expr);
        return;
    case no_serialize:
        if (isDummySerializeDeserialize(expr))
            buildRowAssign(ctx, target, expr->queryChild(0)->queryChild(0));
        else
            doBuildRowAssignSerializeRow(ctx, target, expr);
        return;
    case no_if:
        {
            OwnedHqlExpr foldedCond = foldHqlExpression(expr->queryChild(0));
            if (foldedCond->queryValue())
            {
                unsigned branch = (foldedCond->queryValue()->getBoolValue()) ? 1 : 2;
                buildRowAssign(ctx, target, expr->queryChild(branch));
                return;
            }

            //Assigning a variable size record can mean that references to self need recalculating outside of the condition,
            //producing poor code.
            if (!isVariableSizeRecord(expr->queryRecord()))
            {
                BuildCtx condctx(ctx);
                IHqlStmt * cond = buildFilterViaExpr(condctx, foldedCond);

                buildRowAssign(condctx, target, expr->queryChild(1));
                condctx.selectElse(cond);
                buildRowAssign(condctx, target, expr->queryChild(2));
                return;
            }
        }
        break;
        /*
    case no_externalcall:
        //MORE: Should assign directly to the target, but may not be very easy....
        if (target->isBinary() && queryRecord(source->queryType()) == expr->queryRecord())
        {
            CHqlBoundExpr address;
            target->buildAddress(ctx, address);
            row.setown(createValue(no_typetransfer, makeReferenceModifier(LINK(selector->queryType())), LINK(address.expr)));
            doBuildCall(ctx, &target, expr, NULL);
        }
        break;
        */
    case no_comma:
    case no_compound:
        buildStmt(ctx, expr->queryChild(0));
        buildRowAssign(ctx, target, expr->queryChild(1));
        return;
    }

    Owned<IReferenceSelector> src = buildNewRow(ctx, expr);
    buildRowAssign(ctx, target, src);
}

void HqlCppTranslator::buildRowAssign(BuildCtx & ctx, IReferenceSelector * target, IReferenceSelector * source)
{
    BuildCtx subctx(ctx);
    IHqlExpression * sourceRecord = ::queryRecord(source->queryType());
    IHqlExpression * targetRecord = ::queryRecord(target->queryType());

    //if record structures are identical, then we must just be able to block copy the information across.
    bool useMemcpy = (sourceRecord == targetRecord) && source->isBinary() && !source->isConditional() && 
                     !recordRequiresSerialization(sourceRecord);

    if (useMemcpy)
    {
        if (source->queryRootRow()->isConditional())
        {
            IHqlStmt * ifStmt = subctx.addFilter(source->queryRootRow()->queryBound());
            target->setRow(subctx, source);
            subctx.selectElse(ifStmt);
            target->buildClear(subctx, 0);
        }
        else
            target->setRow(subctx, source);
    }
    else
        buildCompoundAssign(subctx, targetRecord, target, sourceRecord, source->queryExpr());
}

//---------------------------------------------------------------------------
// Dataset selection

IReferenceSelector * HqlCppTranslator::doBuildRowSelectTop(BuildCtx & ctx, IHqlExpression * expr)
{
    //create a temporary
    Owned<ITypeInfo> rowType = makeReferenceModifier(expr->getType());
    OwnedHqlExpr rowExpr = ctx.getTempDeclare(rowType, NULL);
    Owned<BoundRow> row = createBoundRow(expr, rowExpr);
    ctx.associate(*row);                                    // associate here because it is compared inside the loop

    CHqlBoundExpr boundCleared;
#ifdef CREATE_DEAULT_ROW_IF_NULL
    buildDefaultRow(ctx, expr, boundCleared);
#else
    buildNullRow(ctx, expr, boundCleared);
#endif

    OwnedHqlExpr defaultRowPtr = getPointer(boundCleared.expr);

    //Declare row for final level, iterate the appropriate number of times, and then assign and break.
    BuildCtx initctx(ctx);
    initctx.addGroup();         // add a group to allow a temporary to be declared later.
    initctx.addAssign(rowExpr, defaultRowPtr);

    HqlExprAssociation * savedMarker = ctx.associateExpr(queryConditionalRowMarker(), rowExpr);
    BuildCtx iterctx(ctx);

    IHqlExpression * sort = expr->queryChild(0);
    IHqlExpression * dataset = sort->queryChild(0);
    IHqlExpression * sortList = sort->queryChild(1);
    BoundRow * chooseCursor = buildDatasetIterate(iterctx, dataset, false);

    //if (!best) { best=row; } else { if (next < best) best = row; }  Must short-circuit the test of best
    OwnedHqlExpr testBest = createBoolExpr(no_eq, LINK(rowExpr), LINK(defaultRowPtr));
    IHqlStmt * ifStmt = iterctx.addFilter(testBest);
    {
        OwnedHqlExpr source = ensureIteratedRowIsLive(initctx, ctx, iterctx, chooseCursor, dataset, expr);
        OwnedHqlExpr castLeftRow = createValue(no_implicitcast, LINK(rowType), LINK(source));//chooseCursor->queryBound()));
        iterctx.addAssign(rowExpr, castLeftRow);
    }
    iterctx.selectElse(ifStmt);

    CHqlBoundExpr bound;
    buildOrderedCompare(iterctx, dataset, sortList, bound, dataset, expr);
    OwnedHqlExpr compare = createBoolExpr(no_lt, LINK(bound.expr), getZero());
    iterctx.addFilter(compare);
    {
        OwnedHqlExpr source = ensureIteratedRowIsLive(initctx, ctx, iterctx, chooseCursor, dataset, expr);
        OwnedHqlExpr castLeftRow = createValue(no_implicitcast, LINK(rowType), LINK(source));//chooseCursor->queryBound()));
        iterctx.addAssign(rowExpr, castLeftRow);
    }

    ctx.removeAssociation(savedMarker);
    //Set conditional later on, so test in main loop is explicit
#ifndef CREATE_DEAULT_ROW_IF_NULL
    row->setConditional(true);
#endif
    return createReferenceSelector(row);
}


BoundRow * HqlCppTranslator::buildOptimizeSelectFirstRow(BuildCtx & ctx, IHqlExpression * expr)
{
    BoundRow * parentRow = NULL;
    node_operator op = expr->getOperator();
    switch (op)
    {
    case no_compound_childaggregate:
        return buildOptimizeSelectFirstRow(ctx, expr->queryChild(0));
    case no_hqlproject:
    case no_newusertable:
        {
            parentRow = buildOptimizeSelectFirstRow(ctx, expr->queryChild(0));
            if (!parentRow)
                return NULL;
        }
        //fall through
    case no_newaggregate:
        {
            Owned<BoundRow> tempRow = declareTempAnonRow(ctx, ctx, expr);
            Owned<BoundRow> rowBuilder = createRowBuilder(ctx, tempRow);

            Owned<IReferenceSelector> createdRef = createReferenceSelector(rowBuilder);

            BuildCtx subctx(ctx);
            subctx.addGroup();
            if (parentRow)
            {
                if (op == no_hqlproject)
                    bindTableCursor(ctx, expr->queryChild(0), tempRow->queryBound(), no_left, querySelSeq(expr));
                else
                    bindTableCursor(ctx, expr->queryChild(0), tempRow->queryBound(), no_none, NULL);
            }
                
            doBuildRowAssignAggregate(subctx, createdRef, expr);
            finalizeTempRow(ctx, tempRow, rowBuilder);

            return tempRow;
        }
        //
    default:
        return NULL;
    }
}


void HqlCppTranslator::convertBoundDatasetToFirstRow(IHqlExpression * expr, CHqlBoundExpr & bound)
{
    Owned<ITypeInfo> type = makeReferenceModifier(expr->getType());
    ITypeInfo * boundType = bound.queryType();
    if (isArrayRowset(boundType))
    {
        Linked<ITypeInfo> rowType = queryUnqualifiedType(queryRowType(boundType));
        rowType.setown(makeReferenceModifier(LINK(rowType)));
        if (hasLinkedRow(boundType))
            type.setown(setLinkCountedAttr(type, true));
        bound.expr.setown(createValue(no_deref, LINK(rowType), LINK(bound.expr)));
    }
    else if (bound.queryType()->isReference())
        bound.expr.setown(createValue(no_typetransfer, LINK(type), bound.expr.getClear()));
    else
        bound.expr.setown(createValue(no_implicitcast, LINK(type), bound.expr.getClear()));
}

void HqlCppTranslator::convertBoundRowToDataset(BuildCtx & ctx, CHqlBoundExpr & bound, const BoundRow * row, ExpressionFormat preferredFormat)
{
    IHqlExpression * boundRow = row->queryBound();
    IHqlExpression * record = row->queryDataset()->queryRecord();
    Owned<ITypeInfo> type = makeTableType(makeRowType(LINK(record->queryType())), NULL, NULL, NULL);
    Owned<ITypeInfo> refType = makeReferenceModifier(LINK(type));
    if (hasLinkCountedModifier(boundRow->queryType()) && (preferredFormat != FormatBlockedDataset))
    {
        OwnedHqlExpr curActivityId = getCurrentActivityId(ctx);
        StringBuffer allocatorName;
        ensureRowAllocator(allocatorName, ctx, record, curActivityId);

        OwnedHqlExpr src = getPointer(boundRow);
        //We can't just take the address of the link counted row, have to create a temporary dataset
        //could be fixed once the link counting is tracked on rows and datasets
        CHqlBoundTarget target;
        createTempFor(ctx, type, target, typemod_none, FormatLinkedDataset);
        StringBuffer s;
        generateExprCpp(s, target.expr).append(".setRow(").append(allocatorName).append(",");
            generateExprCpp(s, src).append(");");
        ctx.addQuoted(s);
        bound.setFromTarget(target);
    }
    else if (boundRow->queryType()->isReference())
        bound.expr.setown(createValue(no_typetransfer, LINK(refType), LINK(boundRow)));
    else
        bound.expr.setown(createValue(no_implicitcast, LINK(refType), LINK(boundRow)));
    bound.count.setown(getSizetConstant(1));
}

IHqlExpression * HqlCppTranslator::ensureIteratedRowIsLive(BuildCtx & initctx, BuildCtx & searchctx, BuildCtx & iterctx, BoundRow * row, IHqlExpression * dataset, IHqlExpression * rowExpr)
{
    //The problem is that we are iterating through the rows in a dataset, and we need to access the "best" row outside of the loop
    //However subsequent iterations of the loop might invalidate the current row, so we need to ensure the best row is retained.
    //There should really be a better way, but it isn't too bad with link counted rows.
    bool needToPreserve = false;
    IHqlExpression * ds = dataset;
    while (ds && !needToPreserve)
    {
        if (ds->isDatarow())
        {
            if (initctx.queryAssociation(ds, AssocRow, NULL))
                break;
        }
        else
        {
            if (initctx.queryMatchExpr(ds))
                break;
        }

        switch (ds->getOperator())
        {
        case no_filter:
        case no_grouped:
        case no_stepped:
        case no_sorted:
        case no_distributed:
        case no_preservemeta:
        case no_choosen:
        case no_selectnth:                      // can occur as the lhs of no_select
        case no_compound_childnormalize:
        case no_compound_selectnew:
        case no_compound_childread:
        case no_dataset_alias:
            ds = ds->queryChild(0);
            break;
        case no_select:
            if (ds->isDataset())
            {
                if (ds->hasProperty(newAtom))
                {
                    ds = ds->queryChild(0);
                    //don't walk complexds[1].childDataset<new> since the [1] will be generated as a temporary
//                  if (!ds->isDataset() && (ds->getOperator() != no_select))
//                      ds = NULL;
                }
                else
                    ds = NULL;
            }
            else
            {
                //ds.x.y, always walk to to ds.x
                ds = ds->queryChild(0);
            }
            break;
        case no_rows:
        case no_call:
        case no_externalcall:
        case no_getresult:
        case no_getgraphresult:
        case no_alias:
            ds = NULL;
            break;
        default:
            needToPreserve = true;
            break;
        }
    }

    OwnedHqlExpr source = getPointer(row->queryBound());
    if (!needToPreserve || initctx.hasAssociation(*row, false))
        return source.getClear();

    //If link counted, then declare a member that is a link counted row to ensure this row remains linked.
    ITypeInfo * rowType = rowExpr->queryType();
    if (hasLinkCountedModifier(row->queryBound()))
    {
        CHqlBoundTarget saveTarget;
        createTempFor(initctx, rowType, saveTarget, typemod_wrapper, FormatLinkedDataset);
        StringBuffer s;
        generateExprCpp(s, saveTarget.expr);
        s.append(".set(");
        generateExprCpp(s, source).append(");");
        iterctx.addQuoted(s);
        return getPointer(saveTarget.expr);
    }

    BuildCtx childctx(iterctx);
    childctx.addGroup();

    Owned<BoundRow> tempRow = declareTempRow(childctx, childctx, rowExpr);
    Owned<BoundRow> rowBuilder = createRowBuilder(childctx, tempRow);

    OwnedHqlExpr sourceSelector = ensureActiveRow(row->querySelector());
    buildAssign(childctx, rowBuilder->querySelector(), sourceSelector);
    finalizeTempRow(childctx, tempRow, rowBuilder);
    return getPointer(tempRow->queryBound());
}

IReferenceSelector * HqlCppTranslator::buildDatasetIndexViaIterator(BuildCtx & ctx, IHqlExpression * expr)
{
    OwnedHqlExpr dataset = normalizeAnyDatasetAliases(querySkipDatasetMeta(expr->queryChild(0)));
    IHqlExpression * index = expr->queryChild(1);
    IHqlExpression * childDataset = dataset;
    switch (dataset->getOperator())
    {
    case no_hqlproject:
        //optimize selectnth(project(rows, t), n) to projectrow(selectnth(rows, n), t)
        if (dataset->queryChild(1)->isPure() && !expr->hasProperty(_countProject_Atom))
            childDataset = dataset->queryChild(0);
        break;
    }

    //create a temporary
    //Following works because rows are created as temporaries in the class, so still in scope outside the iterate loop.
    //Not a strictly correct assumption - e.g., if ever done in the main process() code.
    Owned<ITypeInfo> rowType = makeReferenceModifier(expr->getType());
    OwnedHqlExpr rowExpr = ctx.getTempDeclare(rowType, NULL);
    Owned<BoundRow> row = createBoundRow(expr, rowExpr);

    CHqlBoundExpr boundCleared;
#ifdef CREATE_DEAULT_ROW_IF_NULL
    buildDefaultRow(ctx, expr, boundCleared);
#else
    buildNullRow(ctx, expr, boundCleared);
    row->setConditional(true);
#endif
    OwnedHqlExpr defaultRowPtr = getPointer(boundCleared.expr);

    //Declare row for final level, iterate the appropriate number of times, and then assign and break.
    BuildCtx initctx(ctx);
    initctx.addGroup();         // add a group to allow a temporary to be declared later.
    initctx.addAssign(rowExpr, defaultRowPtr);
    HqlExprAssociation * savedMarker = ctx.associateExpr(queryConditionalRowMarker(), rowExpr);

    BuildCtx iterctx(ctx);
    bool done = false;
    if (childDataset->getOperator() == no_rows) //hasOutOfLineModifier(dataset->queryType()))
    {
        CHqlBoundExpr boundDs;
        buildDataset(ctx, childDataset, boundDs, FormatNatural);
        if (boundDs.count && isArrayRowset(boundDs.expr->queryType()))
        {
            OwnedHqlExpr castIndex = ensureExprType(index, unsignedType);
            OwnedHqlExpr adjustedIndex = adjustValue(castIndex, -1);
            CHqlBoundExpr boundIndex;
            buildExpr(ctx, adjustedIndex, boundIndex);
            OwnedHqlExpr count = getBoundCount(boundDs);                // could be serialized, so can't assume bound.count is set

            OwnedHqlExpr test = createValue(no_gt, makeBoolType(), LINK(count), LINK(boundIndex.expr));
            iterctx.addFilter(test);
            if (dataset != childDataset)
            {
                Owned<ITypeInfo> datasetRowType = makeRowReferenceType(boundDs);
                OwnedHqlExpr selectedRow = createValue(no_index, LINK(datasetRowType), LINK(boundDs.expr), LINK(boundIndex.expr));
                OwnedHqlExpr projected = createRow(no_projectrow, createTranslated(selectedRow), createComma(LINK(dataset->queryChild(1)), LINK(querySelSeq(dataset))));
                Owned<IReferenceSelector> newRow = buildNewRow(iterctx, projected);
                OwnedHqlExpr newPtr = getPointer(newRow->queryRootRow()->queryBound());
                iterctx.addAssign(rowExpr, newPtr);
            }
            else
            {
                OwnedHqlExpr selectedRow = createValue(no_index, LINK(rowType), LINK(boundDs.expr), LINK(boundIndex.expr));
                iterctx.addAssign(rowExpr, selectedRow);
            }
            done = true;
        }
    }

    if (!done)
    {
        BoundRow * chooseCursor;
        //If choosing the first element, then no need to maintain a counter...
        IValue * indexValue = index->queryValue();
        if (indexValue && (indexValue->getIntValue() == 1))
            chooseCursor = buildDatasetIterate(iterctx, dataset, true);
        else
            chooseCursor = buildDatasetIterate(iterctx, expr, true);
        if (chooseCursor)
        {
            OwnedHqlExpr source = getPointer(chooseCursor->queryBound());

            //MORE: Need casts because cursor may be (probably are) constant, but temporary isn't
            //should somehow fnd out by looking at the cursors.
            OwnedHqlExpr castLeftRow = createValue(no_implicitcast, LINK(rowType), LINK(source));
            iterctx.addAssign(rowExpr, castLeftRow);
            iterctx.addBreak();
        }
    }
    ctx.removeAssociation(savedMarker);
    ctx.associate(*row);
    return createReferenceSelector(row);
}

IReferenceSelector * HqlCppTranslator::buildDatasetIndex(BuildCtx & ctx, IHqlExpression * expr)
{
    HqlExprAssociation * match = ctx.queryAssociation(expr, AssocRow, NULL);
    if (match)
        return createReferenceSelector(static_cast<BoundRow *>(match));

#if 0
    //Causes some queries (ncf10) to run out of memory, so disable for the moment.
    OwnedHqlExpr optimized = optimizeHqlExpression(expr, getOptimizeFlags()|HOOcompoundproject);
    if (optimized != expr)
        return buildNewRow(ctx, optimized);
#endif

    OwnedHqlExpr dataset = normalizeAnyDatasetAliases(expr->queryChild(0));

    //Special cases:
    //i) selecting row [1] from something that only has a single row
    //ii) selecting row [n] from something that can be iterated.
    //iii) row[1] from something sorted that can be iterated.
    BoundRow * row = NULL;
    if (isTrivialSelectN(expr))
    {
        BoundRow * row = NULL;
#if 0
        //This could be a good idea - but again it can mess up cse since dataset never gets bound.
        //Could enable if I implement cse on datasets within transforms.
//          if (canIterateInline(&ctx, dataset))
//              row = buildOptimizeSelectFirstRow(ctx, dataset);
#endif
        if (!row)
        {
            CHqlBoundExpr bound;
            buildDataset(ctx, dataset, bound, FormatNatural);
            convertBoundDatasetToFirstRow(expr, bound);
            row = bindRow(ctx, expr, bound.expr);
        }
        return createReferenceSelector(row);
    }
    else if (canIterateInline(&ctx, dataset))
    {
        //MORE? Following doesn't work for implicit normalize which iterates multiple levels
        bool specialCase = false;
        dataset.set(querySkipDatasetMeta(dataset));
        
        switch (dataset->getOperator())
        {
        case no_select:
            specialCase = !isMultiLevelDatasetSelector(expr, false);
            break;
        case no_if:
        case no_inlinetable:
        case no_join:
            //Always creates a temporary, so don't use an iterator
            specialCase = true;
            break;
        default:
            specialCase = alwaysEvaluatesToBound(dataset);
            break;
        }

        if (!specialCase)
            return buildDatasetIndexViaIterator(ctx, expr);
    }
    else if (isSelectSortedTop(expr) && canIterateInline(&ctx, dataset->queryChild(0)))
    {
        return doBuildRowSelectTop(ctx, expr);
    }
    //MORE: Is this a good idea???
    else if (!canProcessInline(&ctx, expr))
    {
        CHqlBoundExpr bound;
        OwnedHqlExpr dsExpr = expr->isDatarow() ? createDatasetFromRow(LINK(expr)) : LINK(expr);
        buildDataset(ctx, dsExpr, bound, FormatNatural);
        convertBoundDatasetToFirstRow(expr, bound);
        row = bindRow(ctx, expr, bound.expr);
    }

    if (!row)
    {
        Owned<IHqlCppDatasetCursor> cursor = createDatasetSelector(ctx, dataset);
        row = cursor->buildSelect(ctx, expr);

        if (!row)
        {
            CHqlBoundExpr boundCleared;
            buildDefaultRow(ctx, dataset, boundCleared);
            OwnedHqlExpr defaultRowPtr = getPointer(boundCleared.expr);
            row = bindRow(ctx, expr, defaultRowPtr);
        }
    }
    return createReferenceSelector(row);
}

//---------------------------------------------------------------------------

IHqlExpression * HqlCppTranslator::buildGetLocalResult(BuildCtx & ctx, IHqlExpression * expr, bool preferLinkedRows)
{
    IHqlExpression * graphId = expr->queryChild(1);
    IHqlExpression * resultNum = expr->queryChild(2);
    Linked<ITypeInfo> exprType = queryUnqualifiedType(expr->queryType());
    if (preferLinkedRows && !hasLinkCountedModifier(exprType))
        exprType.setown(makeAttributeModifier(LINK(exprType), getLinkCountedAttr()));

    if (expr->hasProperty(externalAtom))
    {
        IHqlExpression * resultInstance = queryPropertyChild(expr, externalAtom, 0);
        HqlExprAssociation * matchedResults = ctx.queryMatchExpr(resultInstance);
        if (!matchedResults)
        {
            //Very unusual - a result is required from a child query, but that child query is actually in
            //the parent/grandparent.  We need to evaluate in the parent instead.
            CHqlBoundExpr match;
            if (!buildExprInCorrectContext(ctx, expr, match, false))
                throwUnexpected();
            return match.getTranslatedExpr();
        }

        HqlExprArray args;
        args.append(*LINK(matchedResults->queryExpr()));
        args.append(*LINK(resultNum));
        if (preferLinkedRows)
            return bindFunctionCall(getChildQueryLinkedResultAtom, args, exprType);
        return bindFunctionCall(getChildQueryResultAtom, args, exprType);
    }

    assertex(activeActivities.ordinality());
    queryAddResultDependancy(activeActivities.tos(), graphId, resultNum);

    SubGraphInfo * activeSubgraph = queryActiveSubGraph(ctx);
    assertex(activeSubgraph && graphId == activeSubgraph->graphTag);
    unique_id_t id = activeSubgraph->graphId;

    EvalContext * instance = queryEvalContext(ctx);
    OwnedHqlExpr retInstanceExpr;
    if (instance && !insideOnCreate(ctx))
        retInstanceExpr.setown(instance->createGraphLookup(id, false));
    else
        retInstanceExpr.setown(doCreateGraphLookup(ctx, ctx, id, "this", true));

    HqlExprArray args;
    args.append(*LINK(retInstanceExpr));
    args.append(*LINK(resultNum));
    if (preferLinkedRows)
        return bindFunctionCall(getLocalLinkedResultAtom, args, exprType);
    return bindFunctionCall(getLocalResultAtom, args, exprType);
}

void HqlCppTranslator::doBuildAssignGetGraphResult(BuildCtx & ctx, const CHqlBoundTarget & target, IHqlExpression * expr)
{
    if (expr->hasProperty(_streaming_Atom))
        throwError(HQLERR_LoopTooComplexForParallel);

    bool isTargetLinkCounted = hasLinkCountedModifier(target.queryType());
    if (expr->hasProperty(externalAtom))
    {
        OwnedHqlExpr call = buildGetLocalResult(ctx, expr, isTargetLinkCounted);
        buildExprAssign(ctx, target, call);
        return;
    }

    if (!isCurrentActiveGraph(ctx, expr->queryChild(1)))
    {
        CHqlBoundExpr match;
        if (!buildExprInCorrectContext(ctx, expr, match, false))
            throwError(HQLERR_GraphContextNotFound);

        assign(ctx, target, match);
        return;
    }

    OwnedHqlExpr call = buildGetLocalResult(ctx, expr, isTargetLinkCounted);
    buildExprAssign(ctx, target, call);
}


void HqlCppTranslator::doBuildExprGetGraphResult(BuildCtx & ctx, IHqlExpression * expr, CHqlBoundExpr & tgt, ExpressionFormat format)
{
    if (!expr->hasProperty(externalAtom))
    {
        doBuildAliasValue(ctx, expr, tgt);
        return;

        if (!isCurrentActiveGraph(ctx, expr->queryChild(1)))
        {
            if (!buildExprInCorrectContext(ctx, expr, tgt, false))
                throwError(HQLERR_GraphContextNotFound);
            return;
        }
    }

    bool useLinkCounted = recordRequiresSerialization(expr->queryRecord()) || options.tempDatasetsUseLinkedRows;

    OwnedHqlExpr call = buildGetLocalResult(ctx, expr, useLinkCounted);
    switch (expr->queryType()->getTypeCode())
    {
    case type_row:
        throwUnexpected();
    case type_table:
    case type_groupedtable:
        buildTempExpr(ctx, call, tgt);
        break;
    default:
        buildExpr(ctx, call, tgt);
        break;
    }
}


ABoundActivity * HqlCppTranslator::doBuildActivityGetGraphResult(BuildCtx & ctx, IHqlExpression * expr)
{
    IHqlExpression * graphId = expr->queryChild(1);
    IHqlExpression * resultNum = expr->queryChild(2);
    ThorActivityKind activityKind = (expr->hasProperty(_streaming_Atom) ? TAKlocalstreamread : TAKlocalresultread);

    bool useImplementationClass = options.minimizeActivityClasses && (resultNum->getOperator() == no_constant);
    Owned<ActivityInstance> instance = new ActivityInstance(*this, ctx, activityKind, expr, "LocalResultRead");
    if (useImplementationClass)
        instance->setImplementationClass(newLocalResultReadArgAtom);
    if (expr->hasProperty(_loop_Atom))
    {
        if (isCurrentActiveGraph(ctx, graphId))
            instance->graphLabel.set("Begin Loop");
        else
            instance->graphLabel.set("Outer Loop Input");
    }
    buildActivityFramework(instance);

    buildInstancePrefix(instance);
    if (!useImplementationClass)
        doBuildUnsignedFunction(instance->classctx, "querySequence", resultNum);
    else
        instance->addConstructorParameter(resultNum);

    addGraphIdAttribute(instance, ctx, graphId);
    buildInstanceSuffix(instance);

    queryAddResultDependancy(*instance->queryBoundActivity(), graphId, resultNum);

    return instance->getBoundActivity();
}


ABoundActivity * HqlCppTranslator::doBuildActivitySetGraphResult(BuildCtx & ctx, IHqlExpression * expr, bool isRoot)
{
    IHqlExpression * dataset = expr->queryChild(0);
    IHqlExpression * graphId = expr->queryChild(1);
    IHqlExpression * resultNum = expr->queryChild(2);
    bool isSpill = expr->hasProperty(_spill_Atom);

    ABoundActivity * parentActivity = activeActivities.ordinality() ? &activeActivities.tos() : NULL;
    Owned<ABoundActivity> boundDataset = buildCachedActivity(ctx, dataset);

    bool useImplementationClass = options.minimizeActivityClasses;
    Owned<ActivityInstance> instance;
    if (expr->getOperator() == no_spillgraphresult)
    {
        instance.setown(new ActivityInstance(*this, ctx, TAKlocalresultspill, expr, "LocalResultSpill"));
    }
    else
    {
        instance.setown(new ActivityInstance(*this, ctx, TAKlocalresultwrite, expr, "LocalResultWrite"));
    }

    if (useImplementationClass)
        instance->setImplementationClass(newLocalResultSpillArgAtom);

    if (expr->hasProperty(_loop_Atom))
        instance->graphLabel.set("End Loop");
    buildActivityFramework(instance, isRoot && !isSpill);

    buildInstancePrefix(instance);

    if (!useImplementationClass)
    {
        doBuildUnsignedFunction(instance->classctx, "querySequence", resultNum);
        doBuildBoolFunction(instance->classctx, "usedOutsideGraph", !isSpill);
    }
    else
    {
        instance->addConstructorParameter(resultNum);
        instance->addConstructorParameter(queryBoolExpr(!isSpill));
    }

    if (parentActivity && !insideRemoteGraph(ctx) && !isSpill)
    {
        const char * relationship;
        if (expr->hasProperty(_loop_Atom))
            relationship = "Body";
        else if (insideRemoteGraph(ctx))
            relationship = "Remote";
        else
            relationship = "Child";

        addDependency(ctx, instance->queryBoundActivity(), parentActivity, childAtom, relationship);
    }

    instance->addAttributeBool("_isSpill", isSpill);
    if (targetRoxie())
        addGraphIdAttribute(instance, ctx, graphId);

    buildInstanceSuffix(instance);

    buildConnectInputOutput(ctx, instance, boundDataset, 0, 0);
    associateRemoteResult(*instance, graphId, resultNum);

    return instance->getBoundActivity();
}


ABoundActivity * HqlCppTranslator::doBuildActivityReturnResult(BuildCtx & ctx, IHqlExpression * expr, bool isRoot)
{
    IHqlExpression * dataset = expr->queryChild(0);

    ABoundActivity * parentActivity = activeActivities.ordinality() ? &activeActivities.tos() : NULL;
    Owned<ABoundActivity> boundDataset = buildCachedActivity(ctx, dataset);

    ThorActivityKind kind;
    const char * helper;
    if (dataset->isDataset())
    {
        kind = TAKdatasetresult;
        helper = "DatasetResult";
    }
    else
    {
        kind = TAKrowresult;
        helper = "RowResult";
    }

    Owned<ActivityInstance> instance = new ActivityInstance(*this, ctx, kind, expr, helper);
    buildActivityFramework(instance, isRoot);

    buildInstancePrefix(instance);
    if (parentActivity && !insideRemoteGraph(ctx))
        addDependency(ctx, instance->queryBoundActivity(), parentActivity, childAtom, "Child");
    buildInstanceSuffix(instance);

    buildConnectInputOutput(ctx, instance, boundDataset, 0, 0);

    return instance->getBoundActivity();
}


void HqlCppTranslator::doBuildAssignLoopCounter(BuildCtx & ctx, const CHqlBoundTarget & target, IHqlExpression * expr)
{
    if (!isCurrentActiveGraph(ctx, expr->queryChild(0)))
    {
        CHqlBoundExpr match;
        if (!buildExprInCorrectContext(ctx, expr, match, false))
            throwError(HQLERR_GraphContextNotFound);

        assign(ctx, target, match);
        return;
    }

    HqlExprArray args;
    OwnedHqlExpr call = bindFunctionCall(getGraphLoopCounterAtom, args);
    buildExprAssign(ctx, target, call);
}


//---------------------------------------------------------------------------

ABoundActivity * HqlCppTranslator::doBuildActivityGetGraphLoopResult(BuildCtx & ctx, IHqlExpression * expr)
{
    IHqlExpression * graphId = expr->queryChild(1);
    IHqlExpression * resultNum = expr->queryChild(2);

    Owned<ActivityInstance> instance = new ActivityInstance(*this, ctx, TAKgraphloopresultread, expr, "GraphLoopResultRead");
    buildActivityFramework(instance);

    buildInstancePrefix(instance);
    doBuildUnsignedFunction(instance->startctx, "querySequence", resultNum);
    addGraphIdAttribute(instance, ctx, graphId);
    buildInstanceSuffix(instance);

    return instance->getBoundActivity();
}


ABoundActivity * HqlCppTranslator::doBuildActivitySetGraphLoopResult(BuildCtx & ctx, IHqlExpression * expr)
{
    IHqlExpression * dataset = expr->queryChild(0);
    IHqlExpression * graphId = expr->queryChild(1);
    bool isSpill = expr->hasProperty(_spill_Atom);

    ABoundActivity * parentActivity = activeActivities.ordinality() ? &activeActivities.tos() : NULL;
    Owned<ABoundActivity> boundDataset = buildCachedActivity(ctx, dataset);

    bool useImplementationClass = options.minimizeActivityClasses;
    Owned<ActivityInstance> instance = new ActivityInstance(*this, ctx, TAKgraphloopresultwrite, expr, "GraphLoopResultWrite");
    if (useImplementationClass)
        instance->setImplementationClass(newGraphLoopResultWriteArgAtom);

    buildActivityFramework(instance, true);

    buildInstancePrefix(instance);
    if (parentActivity && !insideRemoteGraph(ctx) && !isSpill)
        addDependency(ctx, instance->queryBoundActivity(), parentActivity, childAtom, "Body");
    if (targetRoxie())
        addGraphIdAttribute(instance, ctx, graphId);

    buildInstanceSuffix(instance);

    buildConnectInputOutput(ctx, instance, boundDataset, 0, 0);

    return instance->getBoundActivity();
}


//---------------------------------------------------------------------------

static IHqlExpression * queryResultExpr(IHqlExpression * expr)
{
    loop
    {
        switch (expr->getOperator())
        {
        case no_compound:
            expr = expr->queryChild(1);
            break;
        case no_subgraph:
            expr = expr->queryChild(0);
            break;
        case no_returnresult:
            return expr;
        default:
            throwUnexpectedOp(expr->getOperator());
        }
    }
}


ABoundActivity * HqlCppTranslator::doBuildActivityForceLocal(BuildCtx & ctx, IHqlExpression * expr)
{
    IHqlExpression * child = expr->queryChild(0);
    if (targetHThor() || (targetThor() && !insideChildQuery(ctx)))
    {
        WARNING(HQLWRN_LocalHasNoEffect);
        return buildCachedActivity(ctx, child);
    }

    OwnedHqlExpr result = createValue(no_returnresult, makeVoidType(), LINK(child));
    OwnedHqlExpr remote = resourceThorGraph(*this, result, RoxieCluster, 1, NULL);
    unique_id_t localId = doBuildThorSubGraph(ctx, remote, SubGraphRemote);

    Owned<ActivityInstance> instance = new ActivityInstance(*this, ctx, TAKlocalgraph, expr, "Null");
    buildActivityFramework(instance);

    buildInstancePrefix(instance);
    instance->addAttributeInt("_subgraph", localId);

    ActivityAssociation * match = static_cast<ActivityAssociation *>(ctx.queryAssociation(queryResultExpr(remote), AssocActivity, NULL));
    assertex(match);
    addDependency(ctx, match->activity, instance->queryBoundActivity(), childAtom);

    buildInstanceSuffix(instance);

    return instance->getBoundActivity();
}


void HqlCppTranslator::doBuildStmtApply(BuildCtx & ctx, IHqlExpression * expr)
{
    IHqlExpression * dataset = expr->queryChild(0);
    IHqlExpression * start = expr->queryProperty(beforeAtom);
    IHqlExpression * end = expr->queryProperty(afterAtom);

    if (start)
        buildStmt(ctx, start->queryChild(0));
    BuildCtx condctx(ctx);
    BoundRow * cursor = buildDatasetIterate(condctx, dataset, false);
    unsigned max = expr->numChildren();
    for (unsigned i=1; i < max; i++)
    {
        IHqlExpression * cur = expr->queryChild(i);
        if (!cur->isAttribute())
            buildStmt(condctx, cur);
    }

    if (end)
        buildStmt(ctx, end->queryChild(0));
}