Geografic-Information-System/lib/vector/Vlib/write_pg.c

/*!
   \file lib/vector/Vlib/write_pg.c

   \brief Vector library - write vector feature (PostGIS format)

   Higher level functions for reading/writing/manipulating vectors.

   Inspired by OGR PostgreSQL driver.

   \todo PostGIS version of V2__add_line_to_topo_nat()
   \todo OGR version of V2__delete_area_cats_from_cidx_nat()
   \todo function to delete corresponding entry in fidx
   \todo OGR version of V2__add_area_cats_to_cidx_nat
   \todo OGR version of V2__add_line_to_topo_nat

   (C) 2012 by Martin Landa, and the GRASS Development Team

   This program is free software under the GNU General Public License
   (>=v2). Read the file COPYING that comes with GRASS for details.

   \author Martin Landa <landa.martin gmail.com>
 */

#include <string.h>

#include <grass/vector.h>
#include <grass/glocale.h>

#ifdef HAVE_POSTGRES
#include "pg_local_proto.h"

#define WKBSRIDFLAG 0x20000000

static char *binary_to_hex(int, const unsigned char *);
static unsigned char *point_to_wkb(int, const struct line_pnts *, int, int *);
static unsigned char *linestring_to_wkb(int, const struct line_pnts *,
                                        int, int *);
static unsigned char *polygon_to_wkb(int, const struct line_pnts *,
                                     int, int *);
static int write_feature(struct Format_info_pg *,
                         int, const struct line_pnts *, int,
                         int, const struct field_info *);
static char *build_insert_stmt(const struct Format_info_pg *, const char *,
                               int, const struct field_info *);
static char *build_topo_stmt(const struct Format_info_pg *, int, const char *);
static char *build_topogeom_stmt(const struct Format_info_pg *, int, int, int);
static int execute_topo(PGconn *, const char *);
#endif

/*!
   \brief Writes feature on level 1 (PostGIS interface)

   Note:
   - centroids are not supported in PostGIS, pseudotopo holds virtual
   centroids
   - boundaries are not supported in PostGIS, pseudotopo treats polygons
   as boundaries

   \param Map pointer to Map_info structure
   \param type feature type (GV_POINT, GV_LINE, ...)
   \param points pointer to line_pnts structure (feature geometry) 
   \param cats pointer to line_cats structure (feature categories)

   \return feature offset into file
   \return -1 on error
 */
off_t V1_write_line_pg(struct Map_info *Map, int type,
                       const struct line_pnts *points,
                       const struct line_cats *cats)
{
#ifdef HAVE_POSTGRES
    int cat;
    off_t offset;

    SF_FeatureType sf_type;

    struct field_info *Fi;
    struct Format_info_pg *pg_info;
    struct Format_info_offset *offset_info;

    pg_info = &(Map->fInfo.pg);
    offset_info = &(pg_info->offset);

    if (!pg_info->conn) {
        G_warning(_("No connection defined"));
        return -1;
    }

    if (!pg_info->table_name) {
        G_warning(_("PostGIS feature table not defined"));
        return -1;
    }

    if (pg_info->feature_type == SF_UNKNOWN) {
        /* create PostGIS table if doesn't exist */
        if (V2_open_new_pg(Map, type) < 0)
            return -1;
    }

    Fi = NULL;                  /* no attributes to be written */
    cat = -1;
    if (cats->n_cats > 0 && Vect_get_num_dblinks(Map) > 0) {
        /* check for attributes */
        Fi = Vect_get_dblink(Map, 0);
        if (Fi) {
            if (!Vect_cat_get(cats, Fi->number, &cat))
                G_warning(_("No category defined for layer %d"), Fi->number);
            if (cats->n_cats > 1) {
                G_warning(_("Feature has more categories, using "
                            "category %d (from layer %d)"),
                          cat, cats->field[0]);
            }
        }
    }

    sf_type = pg_info->feature_type;

    /* determine matching PostGIS feature geometry type */
    if (type & (GV_POINT | GV_KERNEL)) {
        if (sf_type != SF_POINT && sf_type != SF_POINT25D) {
            G_warning(_("Feature is not a point. Skipping."));
            return -1;
        }
    }
    else if (type & GV_LINE) {
        if (sf_type != SF_LINESTRING && sf_type != SF_LINESTRING25D) {
            G_warning(_("Feature is not a line. Skipping."));
            return -1;
        }
    }
    else if (type & GV_BOUNDARY) {
        if (sf_type != SF_POLYGON) {
            G_warning(_("Feature is not a polygon. Skipping."));
            return -1;
        }
    }
    else if (type & GV_FACE) {
        if (sf_type != SF_POLYGON25D) {
            G_warning(_("Feature is not a face. Skipping."));
            return -1;
        }
    }
    else {
        G_warning(_("Unsupported feature type (%d)"), type);
        return -1;
    }

    G_debug(3, "V1_write_line_pg(): type = %d n_points = %d cat = %d",
            type, points->n_points, cat);

    if (sf_type == SF_POLYGON || sf_type == SF_POLYGON25D) {
        int npoints;

        npoints = points->n_points - 1;
        if (points->x[0] != points->x[npoints] ||
            points->y[0] != points->y[npoints] ||
            points->z[0] != points->z[npoints]) {
            G_warning(_("Boundary is not closed. Skipping."));
            return -1;
        }
    }

    /* write feature's geometry and fid */
    if (-1 == write_feature(pg_info, type, points,
                            Vect_is_3d(Map) ? WITH_Z : WITHOUT_Z, cat, Fi)) {
        execute(pg_info->conn, "ROLLBACK");
        return -1;
    }

    /* update offset array */
    if (offset_info->array_num >= offset_info->array_alloc) {
        offset_info->array_alloc += 1000;
        offset_info->array = (int *)G_realloc(offset_info->array,
                                              offset_info->array_alloc *
                                              sizeof(int));
    }

    offset = offset_info->array_num;

    offset_info->array[offset_info->array_num++] = cat;
    if (sf_type == SF_POLYGON || sf_type == SF_POLYGON25D) {
        /* register first part in offset array */
        offset_info->array[offset_info->array_num++] = 0;
    }
    G_debug(3, "V1_write_line_pg(): -> offset = %lu offset_num = %d cat = %d",
            (unsigned long)offset, offset_info->array_num, cat);

    return offset;
#else
    G_fatal_error(_("GRASS is not compiled with PostgreSQL support"));
    return -1;
#endif
}

/*!
   \brief Rewrites feature at the given offset (level 1) (PostGIS interface)

   \param Map pointer to Map_info structure
   \param offset feature offset
   \param type feature type (GV_POINT, GV_LINE, ...)
   \param points feature geometry
   \param cats feature categories

   \return feature offset (rewriten feature)
   \return -1 on error
 */
off_t V1_rewrite_line_pg(struct Map_info * Map,
                         int line, int type, off_t offset,
                         const struct line_pnts * points,
                         const struct line_cats * cats)
{
    G_debug(3, "V1_rewrite_line_pg(): line=%d type=%d offset=%lu",
            line, type, offset);
#ifdef HAVE_POSTGRES
    if (type != V1_read_line_pg(Map, NULL, NULL, offset)) {
        G_warning(_("Unable to rewrite feature (incompatible feature types)"));
        return -1;
    }

    /* delete old */
    V1_delete_line_pg(Map, offset);

    return V1_write_line_pg(Map, type, points, cats);
#else
    G_fatal_error(_("GRASS is not compiled with PostgreSQL support"));
    return -1;
#endif
}

/*!
   \brief Deletes feature at the given offset (level 1)

   \param Map pointer Map_info structure
   \param offset feature offset

   \return  0 on success
   \return -1 on error
 */
int V1_delete_line_pg(struct Map_info *Map, off_t offset)
{
#ifdef HAVE_POSTGRES
    long fid;
    char stmt[DB_SQL_MAX];

    struct Format_info_pg *pg_info;

    pg_info = &(Map->fInfo.pg);

    if (!pg_info->conn || !pg_info->table_name) {
        G_warning(_("No connection defined"));
        return -1;
    }

    if (offset >= pg_info->offset.array_num) {
        G_warning(_("Invalid offset (%d)"), offset);
        return -1;
    }

    fid = pg_info->offset.array[offset];

    G_debug(3, "V1_delete_line_pg(), offset = %lu -> fid = %ld",
            (unsigned long)offset, fid);

    if (!pg_info->inTransaction) {
        /* start transaction */
        pg_info->inTransaction = TRUE;
        if (execute(pg_info->conn, "BEGIN") == -1)
            return -1;
    }

    sprintf(stmt, "DELETE FROM %s WHERE %s = %ld",
            pg_info->table_name, pg_info->fid_column, fid);
    G_debug(2, "SQL: %s", stmt);

    if (execute(pg_info->conn, stmt) == -1) {
        G_warning(_("Unable to delete feature"));
        execute(pg_info->conn, "ROLLBACK");
        return -1;
    }

    return 0;
#else
    G_fatal_error(_("GRASS is not compiled with PostgreSQL support"));
    return -1;
#endif
}

#ifdef HAVE_POSTGRES
/*!
   \brief Binary data to HEX

   Allocated buffer should be freed by G_free().

   \param nbytes number of bytes to allocate
   \param wkb_data WKB data

   \return allocated buffer with HEX data
 */
char *binary_to_hex(int nbytes, const unsigned char *wkb_data)
{
    char *hex_data;
    int i, nlow, nhigh;
    static const char ach_hex[] = "0123456789ABCDEF";

    hex_data = (char *)G_malloc(nbytes * 2 + 1);
    hex_data[nbytes * 2] = '\0';

    for (i = 0; i < nbytes; i++) {
        nlow = wkb_data[i] & 0x0f;
        nhigh = (wkb_data[i] & 0xf0) >> 4;

        hex_data[i * 2] = ach_hex[nhigh];
        hex_data[i * 2 + 1] = ach_hex[nlow];
    }

    return hex_data;
}

/*!
   \bried Write point into WKB buffer

   See OGRPoint::exportToWkb from GDAL/OGR library

   \param byte_order byte order (ENDIAN_LITTLE or BIG_ENDIAN)
   \param points feature geometry
   \param with_z WITH_Z for 3D data
   \param[out] nsize buffer size

   \return allocated WKB buffer
   \return NULL on error
 */
unsigned char *point_to_wkb(int byte_order,
                            const struct line_pnts *points, int with_z,
                            int *nsize)
{
    unsigned char *wkb_data;
    unsigned int sf_type;

    if (points->n_points != 1)
        return NULL;

    /* allocate buffer */
    *nsize = with_z ? 29 : 21;
    wkb_data = G_malloc(*nsize);
    G_zero(wkb_data, *nsize);

    G_debug(5, "\t->point size=%d (with_z = %d)", *nsize, with_z);

    /* set the byte order */
    if (byte_order == ENDIAN_LITTLE)
        wkb_data[0] = '\001';
    else
        wkb_data[0] = '\000';

    /* set the geometry feature type */
    sf_type = with_z ? SF_POINT25D : SF_POINT;

    if (byte_order == ENDIAN_LITTLE)
        sf_type = LSBWORD32(sf_type);
    else
        sf_type = MSBWORD32(sf_type);
    memcpy(wkb_data + 1, &sf_type, 4);

    /* copy in the raw data */
    memcpy(wkb_data + 5, &(points->x[0]), 8);
    memcpy(wkb_data + 5 + 8, &(points->y[0]), 8);

    if (with_z) {
        memcpy(wkb_data + 5 + 16, &(points->z[0]), 8);
    }

    /* swap if needed */
    if (byte_order == ENDIAN_BIG) {
        SWAPDOUBLE(wkb_data + 5);
        SWAPDOUBLE(wkb_data + 5 + 8);

        if (with_z)
            SWAPDOUBLE(wkb_data + 5 + 16);
    }

    return wkb_data;
}

/*!
   \bried Write linestring into WKB buffer

   See OGRLineString::exportToWkb from GDAL/OGR library

   \param byte_order byte order (ENDIAN_LITTLE or ENDIAN_BIG)
   \param points feature geometry
   \param with_z WITH_Z for 3D data
   \param[out] nsize buffer size

   \return allocated WKB buffer
   \return NULL on error
 */
unsigned char *linestring_to_wkb(int byte_order,
                                 const struct line_pnts *points, int with_z,
                                 int *nsize)
{
    int i, point_size;
    unsigned char *wkb_data;
    unsigned int sf_type;

    if (points->n_points < 1)
        return NULL;

    /* allocate buffer */
    point_size = 8 * (with_z ? 3 : 2);
    *nsize = 5 + 4 + points->n_points * point_size;
    wkb_data = G_malloc(*nsize);
    G_zero(wkb_data, *nsize);

    G_debug(5, "\t->linestring size=%d (with_z = %d)", *nsize, with_z);

    /* set the byte order */
    if (byte_order == ENDIAN_LITTLE)
        wkb_data[0] = '\001';
    else
        wkb_data[0] = '\000';

    /* set the geometry feature type */
    sf_type = with_z ? SF_LINESTRING25D : SF_LINESTRING;

    if (byte_order == ENDIAN_LITTLE)
        sf_type = LSBWORD32(sf_type);
    else
        sf_type = MSBWORD32(sf_type);
    memcpy(wkb_data + 1, &sf_type, 4);

    /* copy in the data count */
    memcpy(wkb_data + 5, &(points->n_points), 4);

    /* copy in the raw data */
    for (i = 0; i < points->n_points; i++) {
        memcpy(wkb_data + 9 + point_size * i, &(points->x[i]), 8);
        memcpy(wkb_data + 9 + 8 + point_size * i, &(points->y[i]), 8);

        if (with_z) {
            memcpy(wkb_data + 9 + 16 + point_size * i, &(points->z[i]), 8);
        }
    }

    /* swap if needed */
    if (byte_order == ENDIAN_BIG) {
        int npoints, nitems;

        npoints = SWAP32(points->n_points);
        memcpy(wkb_data + 5, &npoints, 4);

        nitems = (with_z ? 3 : 2) * points->n_points;
        for (i = 0; i < nitems; i++) {
            SWAPDOUBLE(wkb_data + 9 + 4 + 8 * i);
        }
    }

    return wkb_data;
}

/*!
   \bried Write polygon into WKB buffer

   See OGRPolygon::exportToWkb from GDAL/OGR library

   \param byte_order byte order (ENDIAN_LITTLE or ENDIAN_BIG)
   \param points feature geometry
   \param with_z WITH_Z for 3D data
   \param[out] nsize buffer size

   \return allocated WKB buffer
   \return NULL on error
 */
unsigned char *polygon_to_wkb(int byte_order,
                              const struct line_pnts *points, int with_z,
                              int *nsize)
{
    int i, point_size, nrings;
    unsigned char *wkb_data;
    unsigned int sf_type;

    if (points->n_points < 3)
        return NULL;

    /* allocate buffer */
    point_size = 8 * (with_z ? 3 : 2);
    /* one ring only */
    nrings = 1;
    *nsize = 9 + (4 + point_size * points->n_points);
    wkb_data = G_malloc(*nsize);
    G_zero(wkb_data, *nsize);

    G_debug(5, "\t->polygon size=%d (with_z = %d)", *nsize, with_z);

    /* set the byte order */
    if (byte_order == ENDIAN_LITTLE)
        wkb_data[0] = '\001';
    else
        wkb_data[0] = '\000';

    /* set the geometry feature type */
    sf_type = with_z ? SF_POLYGON25D : SF_POLYGON;

    if (byte_order == ENDIAN_LITTLE)
        sf_type = LSBWORD32(sf_type);
    else
        sf_type = MSBWORD32(sf_type);
    memcpy(wkb_data + 1, &sf_type, 4);

    /* copy in the raw data */
    if (byte_order == ENDIAN_BIG) {
        int ncount;

        ncount = SWAP32(nrings);
        memcpy(wkb_data + 5, &ncount, 4);
    }
    else {
        memcpy(wkb_data + 5, &nrings, 4);
    }

    /* serialize ring */
    memcpy(wkb_data + 9, &(points->n_points), 4);
    for (i = 0; i < points->n_points; i++) {
        memcpy(wkb_data + 9 + 4 + point_size * i, &(points->x[i]), 8);
        memcpy(wkb_data + 9 + 4 + 8 + point_size * i, &(points->y[i]), 8);

        if (with_z) {
            memcpy(wkb_data + 9 + 4 + 16 + point_size * i, &(points->z[i]),
                   8);
        }
    }

    /* swap if needed */
    if (byte_order == ENDIAN_BIG) {
        int npoints, nitems;

        npoints = SWAP32(points->n_points);
        memcpy(wkb_data + 5, &npoints, 4);

        nitems = (with_z ? 3 : 2) * points->n_points;
        for (i = 0; i < nitems; i++) {
            SWAPDOUBLE(wkb_data + 9 + 4 + 8 * i);
        }
    }

    return wkb_data;
}

/*!
   \brief Insert feature into table

   \param pg_info pointer to Format_info_pg struct
   \param type feature type (GV_POINT, GV_LINE, ...)
   \param points pointer to line_pnts struct
   \param with_z WITH_Z for 3D data
   \param cat category number (-1 for no category)
   \param Fi pointer to field_info (attributes to copy, NULL for no attributes)

   \return -1 on error
   \retirn 0 on success
 */
int write_feature(struct Format_info_pg *pg_info,
                  int type, const struct line_pnts *points, int with_z,
                  int cat, const struct field_info *Fi)
{
    int byte_order, nbytes, nsize;
    unsigned int sf_type;
    unsigned char *wkb_data;
    char *stmt, *text_data, *text_data_p, *hex_data;

    if (with_z && pg_info->coor_dim != 3) {
        G_warning(_("Trying to insert 3D data into feature table "
                    "which store 2D data only"));
        return -1;
    }
    if (!with_z && pg_info->coor_dim != 2) {
        G_warning(_("Trying to insert 2D data into feature table "
                    "which store 3D data only"));
        return -1;
    }

    byte_order = dig__byte_order_out();

    /* get wkb data */
    nbytes = -1;
    wkb_data = NULL;
    if (type == GV_POINT)
        wkb_data = point_to_wkb(byte_order, points, with_z, &nbytes);
    else if (type == GV_LINE)
        wkb_data = linestring_to_wkb(byte_order, points, with_z, &nbytes);
    else if (type == GV_BOUNDARY)
        wkb_data = polygon_to_wkb(byte_order, points, with_z, &nbytes);

    if (!wkb_data || nbytes < 1) {
        G_warning(_("Unsupported feature type %d"), type);
        return -1;
    }

    /* When converting to hex, each byte takes 2 hex characters. In
       addition we add in 8 characters to represent the SRID integer
       in hex, and one for a null terminator */
    nsize = nbytes * 2 + 8 + 1;
    text_data = text_data_p = (char *)G_malloc(nsize);

    /* convert the 1st byte, which is the endianess flag, to hex */
    hex_data = binary_to_hex(1, wkb_data);
    strcpy(text_data_p, hex_data);
    G_free(hex_data);
    text_data_p += 2;

    /* get the geom type which is bytes 2 through 5 */
    memcpy(&sf_type, wkb_data + 1, 4);

    /* add the SRID flag if an SRID is provided */
    if (pg_info->srid > 0) {
        unsigned int srs_flag;

        /* change the flag to little endianess */
        srs_flag = LSBWORD32(WKBSRIDFLAG);
        /* apply the flag */
        sf_type = sf_type | srs_flag;
    }

    /* write the geom type which is 4 bytes */
    hex_data = binary_to_hex(4, (unsigned char *)&sf_type);
    strcpy(text_data_p, hex_data);
    G_free(hex_data);
    text_data_p += 8;

    /* include SRID if provided */
    if (pg_info->srid > 0) {
        unsigned int srs_id;

        /* force the srsid to little endianess */
        srs_id = LSBWORD32(pg_info->srid);
        hex_data = binary_to_hex(sizeof(srs_id), (unsigned char *)&srs_id);
        strcpy(text_data_p, hex_data);
        G_free(hex_data);
        text_data_p += 8;
    }

    /* copy the rest of the data over - subtract 5 since we already
       copied 5 bytes above */
    hex_data = binary_to_hex(nbytes - 5, wkb_data + 5);
    strcpy(text_data_p, hex_data);
    G_free(hex_data);

    /* build INSERT statement
       simple feature geometry + attributes
    */
    stmt = build_insert_stmt(pg_info, text_data, cat, Fi);
    G_debug(2, "SQL: %s", stmt);

    if (!pg_info->inTransaction) {
        /* start transaction */
        pg_info->inTransaction = TRUE;
        if (execute(pg_info->conn, "BEGIN") == -1)
            return -1;
    }

    /* stmt can NULL when writing PostGIS topology with no attributes
     * attached */
    if (stmt && execute(pg_info->conn, stmt) == -1) {
        /* rollback transaction */
        execute(pg_info->conn, "ROLLBACK");
        return -1;
    }
    G_free(stmt);
    
    /* write feature in PostGIS topology schema if enabled */
    if (pg_info->toposchema_name) {
        int id, do_update;

        do_update = stmt ? TRUE : FALSE; /* update or insert new record 
                                            to the feature table */
        
        /* insert feature into topology schema (node or edge) */
        stmt = build_topo_stmt(pg_info, type, text_data);
        id = execute_topo(pg_info->conn, stmt);
        if (id == -1) {
            /* rollback transaction */
            execute(pg_info->conn, "ROLLBACK");
            return -1;
        }
        G_free(stmt);

        /* insert topoelement into feature table) */
        stmt = build_topogeom_stmt(pg_info, id, type, do_update);
        if (execute(pg_info->conn, stmt) == -1) {
            /* rollback transaction */
            execute(pg_info->conn, "ROLLBACK");
            return -1;
        }
        G_free(stmt);
    }

    G_free(wkb_data);
    G_free(text_data);
    
    return 0;
}

/*!
   \brief Build INSERT statement to insert new feature to the table

   \param pg_info pointer to Format_info_pg structure
   \param cat category number (or -1 for no category)
   \param Fi pointer to field_info structure (NULL for no attributes)

   \return allocated string with INSERT statement
 */
char *build_insert_stmt(const struct Format_info_pg *pg_info,
                        const char *geom_data,
                        int cat, const struct field_info *Fi)
{
    char *stmt, buf[DB_SQL_MAX];

    stmt = NULL;
    if (Fi && cat > -1) {
        int col, ncol, more;
        int sqltype, ctype;
        char buf_val[DB_SQL_MAX], buf_tmp[DB_SQL_MAX];
        char *str_val;

        const char *colname;

        dbString dbstmt;
        dbCursor cursor;
        dbTable *table;
        dbColumn *column;
        dbValue *value;

        db_init_string(&dbstmt);
        buf_val[0] = '\0';

        /* read & set attributes */
        sprintf(buf, "SELECT * FROM %s WHERE %s = %d", Fi->table, Fi->key,
                cat);
        G_debug(4, "SQL: %s", buf);
        db_set_string(&dbstmt, buf);

        /* prepare INSERT statement */
        sprintf(buf, "INSERT INTO \"%s\".\"%s\" (",
                pg_info->schema_name, pg_info->table_name);
        
        /* select data */
        if (db_open_select_cursor(pg_info->dbdriver, &dbstmt,
                                  &cursor, DB_SEQUENTIAL) != DB_OK) {
            G_warning(_("Unable to select attributes for category %d"), cat);
        }
        else {
            if (db_fetch(&cursor, DB_NEXT, &more) != DB_OK) {
                G_warning(_("Unable to fetch data from table <%s>"),
                          Fi->table);
            }

            if (!more) {
                G_warning(_("No database record for category %d, "
                            "no attributes will be written"), cat);
            }
            else {
                table = db_get_cursor_table(&cursor);
                ncol = db_get_table_number_of_columns(table);

                for (col = 0; col < ncol; col++) {
                    column = db_get_table_column(table, col);
                    colname = db_get_column_name(column);

                    /* skip fid column */
                    if (strcmp(pg_info->fid_column, colname) == 0)
                        continue;

                    /* -> columns */
                    sprintf(buf_tmp, "%s", colname);
                    strcat(buf, buf_tmp);
                    if (col < ncol - 1)
                        strcat(buf, ",");
                    
                    /* -> values */
                    value = db_get_column_value(column);
                    /* for debug only */
                    db_convert_column_value_to_string(column, &dbstmt);
                    G_debug(2, "col %d : val = %s", col,
                            db_get_string(&dbstmt));

                    sqltype = db_get_column_sqltype(column);
                    ctype = db_sqltype_to_Ctype(sqltype);

                    /* prevent writing NULL values */
                    if (!db_test_value_isnull(value)) {
                        switch (ctype) {
                        case DB_C_TYPE_INT:
                            sprintf(buf_tmp, "%d", db_get_value_int(value));
                            break;
                        case DB_C_TYPE_DOUBLE:
                            sprintf(buf_tmp, "%.14f",
                                    db_get_value_double(value));
                            break;
                        case DB_C_TYPE_STRING:
                            str_val = G_store(db_get_value_string(value));
                            G_str_to_sql(str_val);
                            sprintf(buf_tmp, "'%s'", str_val);
                            G_free(str_val);
                            break;
                        case DB_C_TYPE_DATETIME:
                            db_convert_column_value_to_string(column,
                                                              &dbstmt);
                            sprintf(buf_tmp, "%s", db_get_string(&dbstmt));
                            break;
                        default:
                            G_warning(_("Unsupported column type %d"), ctype);
                            sprintf(buf_tmp, "NULL");
                            break;
                        }
                    }
                    else {
                        sprintf(buf_tmp, "NULL");
                    }
                    strcat(buf_val, buf_tmp);
                    if (col < ncol - 1)
                        strcat(buf_val, ",");
                }
                
                if (!pg_info->toposchema_name) {
                    /* simple feature access */
                    G_asprintf(&stmt, "%s,%s) VALUES (%s,'%s'::GEOMETRY)",
                               buf, pg_info->geom_column, buf_val, geom_data);
                }
                else {
                    /* PostGIS topology access, write geometry in
                     * topology schema, skip geometry at this point */
                    G_asprintf(&stmt, "%s) VALUES (%s)",
                               buf, buf_val);
                }
            }
        }
    }
    else if (pg_info->toposchema_name)
        return NULL; /* don't write simple feature element */

    if (!stmt) {
        /* no attributes */
        G_asprintf(&stmt, "INSERT INTO \"%s\".\"%s\" (%s) VALUES "
                   "('%s'::GEOMETRY)",
                   pg_info->schema_name, pg_info->table_name,
                   pg_info->geom_column, geom_data);
    }

    return stmt;
}

/*!
  \brief Build SELECT statement to insert new element into PostGIS
  topology schema

  \param pg_info so pointer to Format_info_pg
  \param type feature type (GV_POINT, ...)
  \param geom_data geometry in wkb

  \return pointer to allocated string buffer with SQL statement
  \return NULL on error
*/
char *build_topo_stmt(const struct Format_info_pg *pg_info,
                      int type, const char *geom_data)
{
    char *stmt;
    
    stmt = NULL;
    if (type == GV_POINT) {
        G_asprintf(&stmt, "SELECT AddNode('%s', '%s'::GEOMETRY)",
                pg_info->toposchema_name, geom_data);
    }
    
    return stmt;
}

/*!
  \brief Build INSERT / UPDATE statement to insert topo geometry
  object into feature table

  Allocated string should be freed by G_free()
  
  \param pg_info so pointer to Format_info_pg
  \param type feature type (GV_POINT, ...)
  \param id topology element id
  \param do_update TRUE for UPDATE otherwise build SELECT statement
  
  \return pointer to allocated string buffer with SQL statement
  \return NULL on error
*/
char *build_topogeom_stmt(const struct Format_info_pg *pg_info,
                          int id, int type, int do_update)
{
    int topogeom_type;
    char *stmt;
    
    stmt = NULL;

    if (type == GV_POINT)
        topogeom_type = 1;
    else if (type == GV_LINES)
        topogeom_type = 2;
    else {
        G_warning(_("Unsupported topo geometry type %d"), type);
        return NULL;
    }
    
    if (!do_update)
        G_asprintf(&stmt, "INSERT INTO \"%s\".\"%s\" (%s) VALUES "
                   "(topology.CreateTopoGeom('%s', 1, %d, "
                   "'{{%d, %d}}'::topology.topoelementarray))",
                   pg_info->schema_name, pg_info->table_name,
                   pg_info->topogeom_column, pg_info->toposchema_name,
                   topogeom_type, id, topogeom_type);
    else
        G_asprintf(&stmt, "UPDATE \"%s\".\"%s\" SET %s = "
                   "topology.CreateTopoGeom('%s', 1, %d, "
                   "'{{%d, %d}}'::topology.topoelementarray) "
                   "WHERE %s = %d",
                   pg_info->schema_name, pg_info->table_name,
                   pg_info->topogeom_column, pg_info->toposchema_name,
                   topogeom_type, id, topogeom_type,
                   pg_info->fid_column, id);
    
    return stmt;
}

/*!
   \brief Execute SQL topo select statement

   \param conn pointer to PGconn
   \param stmt query

   \return value on success
   \return -1 on error
 */
int execute_topo(PGconn *conn, const char *stmt)
{
    int ret;
    PGresult *result;

    result = NULL;

    G_debug(3, "execute_topo(): %s", stmt);
    result = PQexec(conn, stmt);
    if (!result || PQresultStatus(result) != PGRES_TUPLES_OK ||
        PQntuples(result) != 1) {
        PQclear(result);

        G_warning(_("Execution failed: %s"), PQerrorMessage(conn));
        return -1;
    }

    ret = atoi(PQgetvalue(result, 0, 0));
    PQclear(result);
    
    return ret;
}
   
#endif