Create executor and planner-backend support for decoupled heap and index

scans, using in-memory tuple ID bitmaps as the intermediary.  The planner
frontend (path creation and cost estimation) is not there yet, so none
of this code can be executed.  I have tested it using some hacked planner
code that is far too ugly to see the light of day, however.  Committing
now so that the bulk of the infrastructure changes go in before the tree
drifts under me.

src/backend/executor/nodeBitmapAnd.c

@@ -0,0 +1,208 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeBitmapAnd.c
+ *	  routines to handle BitmapAnd nodes.
+ *
+ * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeBitmapAnd.c,v 1.1 2005/04/19 22:35:12 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+/* INTERFACE ROUTINES
+ *		ExecInitBitmapAnd	- initialize the BitmapAnd node
+ *		MultiExecBitmapAnd	- retrieve the result bitmap from the node
+ *		ExecEndBitmapAnd	- shut down the BitmapAnd node
+ *		ExecReScanBitmapAnd	- rescan the BitmapAnd node
+ *
+ *	 NOTES
+ *		BitmapAnd nodes don't make use of their left and right
+ *		subtrees, rather they maintain a list of subplans,
+ *		much like Append nodes.  The logic is much simpler than
+ *		Append, however, since we needn't cope with forward/backward
+ *		execution.
+ */
+
+#include "postgres.h"
+
+#include "executor/execdebug.h"
+#include "executor/instrument.h"
+#include "executor/nodeBitmapAnd.h"
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitBitmapAnd
+ *
+ *		Begin all of the subscans of the BitmapAnd node.
+ * ----------------------------------------------------------------
+ */
+BitmapAndState *
+ExecInitBitmapAnd(BitmapAnd *node, EState *estate)
+{
+	BitmapAndState *bitmapandstate = makeNode(BitmapAndState);
+	PlanState **bitmapplanstates;
+	int			nplans;
+	int			i;
+	Plan	   *initNode;
+
+	CXT1_printf("ExecInitBitmapAnd: context is %d\n", CurrentMemoryContext);
+
+	/*
+	 * Set up empty vector of subplan states
+	 */
+	nplans = list_length(node->bitmapplans);
+
+	bitmapplanstates = (PlanState **) palloc0(nplans * sizeof(PlanState *));
+
+	/*
+	 * create new BitmapAndState for our BitmapAnd node
+	 */
+	bitmapandstate->ps.plan = (Plan *) node;
+	bitmapandstate->ps.state = estate;
+	bitmapandstate->bitmapplans = bitmapplanstates;
+	bitmapandstate->nplans = nplans;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * BitmapAnd plans don't have expression contexts because they never call
+	 * ExecQual or ExecProject.  They don't need any tuple slots either.
+	 */
+
+#define BITMAPAND_NSLOTS 0
+
+	/*
+	 * call ExecInitNode on each of the plans to be executed and save the
+	 * results into the array "bitmapplanstates".
+	 */
+	for (i = 0; i < nplans; i++)
+	{
+		initNode = (Plan *) list_nth(node->bitmapplans, i);
+		bitmapplanstates[i] = ExecInitNode(initNode, estate);
+	}
+
+	return bitmapandstate;
+}
+
+int
+ExecCountSlotsBitmapAnd(BitmapAnd *node)
+{
+	ListCell   *plan;
+	int			nSlots = 0;
+
+	foreach(plan, node->bitmapplans)
+		nSlots += ExecCountSlotsNode((Plan *) lfirst(plan));
+	return nSlots + BITMAPAND_NSLOTS;
+}
+
+/* ----------------------------------------------------------------
+ *	   MultiExecBitmapAnd
+ * ----------------------------------------------------------------
+ */
+Node *
+MultiExecBitmapAnd(BitmapAndState *node)
+{
+	PlanState **bitmapplans;
+	int			nplans;
+	int			i;
+	TIDBitmap  *result = NULL;
+
+	/* must provide our own instrumentation support */
+	if (node->ps.instrument)
+		InstrStartNode(node->ps.instrument);
+
+	/*
+	 * get information from the node
+	 */
+	bitmapplans = node->bitmapplans;
+	nplans = node->nplans;
+
+	/*
+	 * Scan all the subplans and AND their result bitmaps
+	 */
+	for (i = 0; i < nplans; i++)
+	{
+		PlanState  *subnode = bitmapplans[i];
+		TIDBitmap  *subresult;
+
+		subresult = (TIDBitmap *) MultiExecProcNode(subnode);
+
+		if (!subresult || !IsA(subresult, TIDBitmap))
+			elog(ERROR, "unrecognized result from subplan");
+
+		if (result == NULL)
+			result = subresult;			/* first subplan */
+		else
+		{
+			tbm_intersect(result, subresult);
+			tbm_free(subresult);
+		}
+	}
+
+	if (result == NULL)
+		elog(ERROR, "BitmapAnd doesn't support zero inputs");
+
+	/* must provide our own instrumentation support */
+	if (node->ps.instrument)
+		InstrStopNodeMulti(node->ps.instrument, 0 /* XXX */);
+
+	return (Node *) result;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndBitmapAnd
+ *
+ *		Shuts down the subscans of the BitmapAnd node.
+ *
+ *		Returns nothing of interest.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndBitmapAnd(BitmapAndState *node)
+{
+	PlanState **bitmapplans;
+	int			nplans;
+	int			i;
+
+	/*
+	 * get information from the node
+	 */
+	bitmapplans = node->bitmapplans;
+	nplans = node->nplans;
+
+	/*
+	 * shut down each of the subscans (that we've initialized)
+	 */
+	for (i = 0; i < nplans; i++)
+	{
+		if (bitmapplans[i])
+			ExecEndNode(bitmapplans[i]);
+	}
+}
+
+void
+ExecReScanBitmapAnd(BitmapAndState *node, ExprContext *exprCtxt)
+{
+	int			i;
+
+	for (i = 0; i < node->nplans; i++)
+	{
+		PlanState  *subnode = node->bitmapplans[i];
+
+		/*
+		 * ExecReScan doesn't know about my subplans, so I have to do
+		 * changed-parameter signaling myself.
+		 */
+		if (node->ps.chgParam != NULL)
+			UpdateChangedParamSet(subnode, node->ps.chgParam);
+
+		/*
+		 * Always rescan the inputs immediately, to ensure we can pass down
+		 * any outer tuple that might be used in index quals.
+		 */
+		ExecReScan(subnode, exprCtxt);
+	}
+}