Minor performance improvement: avoid unnecessary creation/unioning of

bitmaps for multiple indexscans.  Instead just let each indexscan add
TIDs directly into the BitmapOr node's result bitmap.

Author: tglsfdc

src/backend/executor/nodeBitmapAnd.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeBitmapAnd.c,v 1.1 2005/04/19 22:35:12 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeBitmapAnd.c,v 1.2 2005/04/20 15:48:36 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -46,6 +46,7 @@ ExecInitBitmapAnd(BitmapAnd *node, EState *estate)
 	PlanState **bitmapplanstates;
 	int			nplans;
 	int			i;
+	ListCell   *l;
 	Plan	   *initNode;
 
 	CXT1_printf("ExecInitBitmapAnd: context is %d\n", CurrentMemoryContext);
@@ -78,10 +79,12 @@ ExecInitBitmapAnd(BitmapAnd *node, EState *estate)
 	 * call ExecInitNode on each of the plans to be executed and save the
 	 * results into the array "bitmapplanstates".
 	 */
-	for (i = 0; i < nplans; i++)
+	i = 0;
+	foreach(l, node->bitmapplans)
 	{
-		initNode = (Plan *) list_nth(node->bitmapplans, i);
+		initNode = (Plan *) lfirst(l);
 		bitmapplanstates[i] = ExecInitNode(initNode, estate);
+		i++;
 	}
 
 	return bitmapandstate;

src/backend/executor/nodeBitmapIndexscan.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeBitmapIndexscan.c,v 1.1 2005/04/19 22:35:12 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeBitmapIndexscan.c,v 1.2 2005/04/20 15:48:36 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -63,9 +63,21 @@ MultiExecBitmapIndexScan(BitmapIndexScanState *node)
 	scandesc = node->biss_ScanDesc;
 
 	/*
-	 * Prepare result bitmap
+	 * Prepare the result bitmap.  Normally we just create a new one to pass
+	 * back; however, our parent node is allowed to store a pre-made one
+	 * into node->biss_result, in which case we just OR our tuple IDs into
+	 * the existing bitmap.  (This saves needing explicit UNION steps.)
 	 */
-	tbm = tbm_create(work_mem * 1024L);
+	if (node->biss_result)
+	{
+		tbm = node->biss_result;
+		node->biss_result = NULL;		/* reset for next time */
+	}
+	else
+	{
+		/* XXX should we use less than work_mem for this? */
+		tbm = tbm_create(work_mem * 1024L);
+	}
 
 	/*
 	 * Get TIDs from index and insert into bitmap
@@ -271,6 +283,9 @@ ExecInitBitmapIndexScan(BitmapIndexScan *node, EState *estate)
 	indexstate->ss.ps.plan = (Plan *) node;
 	indexstate->ss.ps.state = estate;
 
+	/* normally we don't make the result bitmap till runtime */
+	indexstate->biss_result = NULL;
+
 	/*
 	 * Miscellaneous initialization
 	 *

src/backend/executor/nodeBitmapOr.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeBitmapOr.c,v 1.1 2005/04/19 22:35:12 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeBitmapOr.c,v 1.2 2005/04/20 15:48:36 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -31,6 +31,7 @@
 #include "executor/execdebug.h"
 #include "executor/instrument.h"
 #include "executor/nodeBitmapOr.h"
+#include "miscadmin.h"
 
 
 /* ----------------------------------------------------------------
@@ -46,6 +47,7 @@ ExecInitBitmapOr(BitmapOr *node, EState *estate)
 	PlanState **bitmapplanstates;
 	int			nplans;
 	int			i;
+	ListCell   *l;
 	Plan	   *initNode;
 
 	CXT1_printf("ExecInitBitmapOr: context is %d\n", CurrentMemoryContext);
@@ -78,10 +80,12 @@ ExecInitBitmapOr(BitmapOr *node, EState *estate)
 	 * call ExecInitNode on each of the plans to be executed and save the
 	 * results into the array "bitmapplanstates".
 	 */
-	for (i = 0; i < nplans; i++)
+	i = 0;
+	foreach(l, node->bitmapplans)
 	{
-		initNode = (Plan *) list_nth(node->bitmapplans, i);
+		initNode = (Plan *) lfirst(l);
 		bitmapplanstates[i] = ExecInitNode(initNode, estate);
+		i++;
 	}
 
 	return bitmaporstate;
@@ -128,17 +132,41 @@ MultiExecBitmapOr(BitmapOrState *node)
 		PlanState  *subnode = bitmapplans[i];
 		TIDBitmap  *subresult;
 
-		subresult = (TIDBitmap *) MultiExecProcNode(subnode);
+		/*
+		 * We can special-case BitmapIndexScan children to avoid an
+		 * explicit tbm_union step for each child: just pass down the
+		 * current result bitmap and let the child OR directly into it.
+		 */
+		if (IsA(subnode, BitmapIndexScanState))
+		{
+			if (result == NULL)				/* first subplan */
+			{
+				/* XXX should we use less than work_mem for this? */
+				result = tbm_create(work_mem * 1024L);
+			}
+
+			((BitmapIndexScanState *) subnode)->biss_result = result;
 
-		if (!subresult || !IsA(subresult, TIDBitmap))
-			elog(ERROR, "unrecognized result from subplan");
+			subresult = (TIDBitmap *) MultiExecProcNode(subnode);
 
-		if (result == NULL)
-			result = subresult;			/* first subplan */
+			if (subresult != result)
+				elog(ERROR, "unrecognized result from subplan");
+		}
 		else
 		{
-			tbm_union(result, subresult);
-			tbm_free(subresult);
+			/* standard implementation */
+			subresult = (TIDBitmap *) MultiExecProcNode(subnode);
+
+			if (!subresult || !IsA(subresult, TIDBitmap))
+				elog(ERROR, "unrecognized result from subplan");
+
+			if (result == NULL)
+				result = subresult;			/* first subplan */
+			else
+			{
+				tbm_union(result, subresult);
+				tbm_free(subresult);
+			}
 		}
 	}
 

src/include/nodes/execnodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.126 2005/04/19 22:35:17 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.127 2005/04/20 15:48:36 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -901,6 +901,7 @@ typedef struct IndexScanState
 /* ----------------
  *	 BitmapIndexScanState information
  *
+ *		result			   bitmap to return output into, or NULL
  *		ScanKeys		   Skey structures to scan index rel
  *		NumScanKeys		   number of Skey structs
  *		RuntimeKeyInfo	   array of exprstates for Skeys
@@ -914,6 +915,7 @@ typedef struct IndexScanState
 typedef struct BitmapIndexScanState
 {
 	ScanState	ss;				/* its first field is NodeTag */
+	TIDBitmap  *biss_result;
 	ScanKey		biss_ScanKeys;
 	int			biss_NumScanKeys;
 	ExprState **biss_RuntimeKeyInfo;