HPCC-18001 Mark disk read activities as 'fastThrough'

Some activities, notably disk read type activities, were not
marked as 'fastThrough'. Related to HPCC-17991.

Signed-off-by: Jake Smith <jake.smith@lexisnexisrisk.com>

thorlcr/activities/csvread/thcsvrslave.cpp

@@ -385,6 +385,7 @@ public:
             cachedMetaInfo.isSource = true;
             getPartsMetaInfo(cachedMetaInfo, partDescs.ordinality(), partDescs.getArray(), partHandler);
             cachedMetaInfo.unknownRowsOutput = true; // at least I don't think we know
+            cachedMetaInfo.fastThrough = true;
         }
         info = cachedMetaInfo;
     }

thorlcr/activities/diskread/thdiskreadslave.cpp

@@ -466,6 +466,7 @@ public:
             initMetaInfo(cachedMetaInfo);
             cachedMetaInfo.isSource = true;
             getPartsMetaInfo(cachedMetaInfo, partDescs.ordinality(), partDescs.getArray(), partHandler);
+            cachedMetaInfo.fastThrough = true;
         }
         info = cachedMetaInfo;
         if (info.totalRowsMin==info.totalRowsMax)
@@ -877,6 +878,8 @@ public:
     {
         initMetaInfo(info);
         info.isSource = true;
+        if (totalCountKnown)
+            info.fastThrough = true;
         // MORE TBD
     }
     virtual bool isGrouped() const override { return false; }

thorlcr/activities/nsplitter/thnsplitterslave.cpp

@@ -379,7 +379,6 @@ public:
     virtual void getMetaInfo(ThorDataLinkMetaInfo &info) override
     {
         initMetaInfo(info);
-        info.fastThrough = true;
         info.unknownRowsOutput = true;  // remove once calcMetaInfoSize() is called
 
         //GH->JCS I think the following line is correct and may remove some downstream spilling streams

thorlcr/activities/xmlread/thxmlreadslave.cpp

@@ -279,6 +279,7 @@ public:
             cachedMetaInfo.isSource = true;
             getPartsMetaInfo(cachedMetaInfo, partDescs.ordinality(), partDescs.getArray(), partHandler);
             cachedMetaInfo.unknownRowsOutput = true; // at least I don't think we know
+            cachedMetaInfo.fastThrough = true;
         }
         info = cachedMetaInfo;
     }