Major revision of sort-node handling: push knowledge of query

sort order down into planner, instead of handling it only at the very top
level of the planner.  This fixes many things.  An explicit sort is now
avoided if there is a cheaper alternative (typically an indexscan) not
only for ORDER BY, but also for the internal sort of GROUP BY.  It works
even when there is no other reason (such as a WHERE condition) to consider
the indexscan.  It works for indexes on functions.  It works for indexes
on functions, backwards.  It's just so cool...

CAUTION: I have changed the representation of SortClause nodes, therefore
THIS UPDATE BREAKS STORED RULES.  You will need to initdb.

1 files changed, 31 insertions, 20 deletions

diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index fc95d2ce5bc..b600c0e3a8f 100644
--- a/src/backend/executor/nodeAgg.c
+++ b/src/backend/executor/nodeAgg.c
@@ -23,6 +23,7 @@
 #include "executor/executor.h"
 #include "executor/nodeAgg.h"
 #include "optimizer/clauses.h"
+#include "optimizer/planmain.h"
 #include "parser/parse_type.h"
 #include "utils/syscache.h"
 
@@ -91,7 +92,7 @@ ExecAgg(Agg *node)
 	EState	   *estate;
 	Plan	   *outerPlan;
 	int			aggno,
-				nagg;
+				numaggs;
 	Datum	   *value1,
 			   *value2;
 	int		   *noInitValue;
@@ -128,19 +129,19 @@ ExecAgg(Agg *node)
 		estate = node->plan.state;
 		econtext = aggstate->csstate.cstate.cs_ExprContext;
 
-		nagg = length(node->aggs);
+		numaggs = length(aggstate->aggs);
 
 		value1 = node->aggstate->csstate.cstate.cs_ExprContext->ecxt_values;
 		nulls = node->aggstate->csstate.cstate.cs_ExprContext->ecxt_nulls;
 
-		value2 = (Datum *) palloc(sizeof(Datum) * nagg);
-		MemSet(value2, 0, sizeof(Datum) * nagg);
+		value2 = (Datum *) palloc(sizeof(Datum) * numaggs);
+		MemSet(value2, 0, sizeof(Datum) * numaggs);
 
-		aggFuncInfo = (AggFuncInfo *) palloc(sizeof(AggFuncInfo) * nagg);
-		MemSet(aggFuncInfo, 0, sizeof(AggFuncInfo) * nagg);
+		aggFuncInfo = (AggFuncInfo *) palloc(sizeof(AggFuncInfo) * numaggs);
+		MemSet(aggFuncInfo, 0, sizeof(AggFuncInfo) * numaggs);
 
-		noInitValue = (int *) palloc(sizeof(int) * nagg);
-		MemSet(noInitValue, 0, sizeof(int) * nagg);
+		noInitValue = (int *) palloc(sizeof(int) * numaggs);
+		MemSet(noInitValue, 0, sizeof(int) * numaggs);
 
 		outerPlan = outerPlan(node);
 		oneTuple = NULL;
@@ -148,7 +149,7 @@ ExecAgg(Agg *node)
 		projInfo = aggstate->csstate.cstate.cs_ProjInfo;
 
 		aggno = -1;
-		foreach(alist, node->aggs)
+		foreach(alist, aggstate->aggs)
 		{
 			Aggref	   *aggref = lfirst(alist);
 			char	   *aggname;
@@ -269,7 +270,7 @@ ExecAgg(Agg *node)
 			}
 
 			aggno = -1;
-			foreach(alist, node->aggs)
+			foreach(alist, aggstate->aggs)
 			{
 				Aggref	   *aggref = lfirst(alist);
 				AggFuncInfo *aggfns = &aggFuncInfo[++aggno];
@@ -367,7 +368,7 @@ ExecAgg(Agg *node)
 		 */
 
 		aggno = -1;
-		foreach(alist, node->aggs)
+		foreach(alist, aggstate->aggs)
 		{
 			char	   *args[2];
 			AggFuncInfo *aggfns = &aggFuncInfo[++aggno];
@@ -467,6 +468,7 @@ ExecInitAgg(Agg *node, EState *estate, Plan *parent)
 	AggState   *aggstate;
 	Plan	   *outerPlan;
 	ExprContext *econtext;
+	int			numaggs;
 
 	/*
 	 * assign the node's execution state
@@ -478,7 +480,16 @@ ExecInitAgg(Agg *node, EState *estate, Plan *parent)
 	 */
 	aggstate = makeNode(AggState);
 	node->aggstate = aggstate;
-	aggstate->agg_done = FALSE;
+	aggstate->agg_done = false;
+
+	/*
+	 * find aggregates in targetlist and quals
+	 */
+	aggstate->aggs = nconc(pull_agg_clause((Node *) node->plan.targetlist),
+						   pull_agg_clause((Node *) node->plan.qual));
+	numaggs = length(aggstate->aggs);
+	if (numaggs <= 0)
+		elog(ERROR, "ExecInitAgg: could not find any aggregate functions");
 
 	/*
 	 * assign node's base id and create expression context
@@ -495,10 +506,10 @@ ExecInitAgg(Agg *node, EState *estate, Plan *parent)
 	ExecInitResultTupleSlot(estate, &aggstate->csstate.cstate);
 
 	econtext = aggstate->csstate.cstate.cs_ExprContext;
-	econtext->ecxt_values = (Datum *) palloc(sizeof(Datum) * length(node->aggs));
-	MemSet(econtext->ecxt_values, 0, sizeof(Datum) * length(node->aggs));
-	econtext->ecxt_nulls = (char *) palloc(sizeof(char) * length(node->aggs));
-	MemSet(econtext->ecxt_nulls, 0, sizeof(char) * length(node->aggs));
+	econtext->ecxt_values = (Datum *) palloc(sizeof(Datum) * numaggs);
+	MemSet(econtext->ecxt_values, 0, sizeof(Datum) * numaggs);
+	econtext->ecxt_nulls = (char *) palloc(sizeof(char) * numaggs);
+	MemSet(econtext->ecxt_nulls, 0, sizeof(char) * numaggs);
 
 	/*
 	 * initializes child nodes
@@ -510,7 +521,7 @@ ExecInitAgg(Agg *node, EState *estate, Plan *parent)
 	 * Result runs in its own context, but make it use our aggregates fix
 	 * for 'select sum(2+2)'
 	 */
-	if (nodeTag(outerPlan) == T_Result)
+	if (IsA(outerPlan, Result))
 	{
 		((Result *) outerPlan)->resstate->cstate.cs_ProjInfo->pi_exprContext->ecxt_values =
 			econtext->ecxt_values;
@@ -645,9 +656,9 @@ ExecReScanAgg(Agg *node, ExprContext *exprCtxt, Plan *parent)
 	AggState   *aggstate = node->aggstate;
 	ExprContext *econtext = aggstate->csstate.cstate.cs_ExprContext;
 
-	aggstate->agg_done = FALSE;
-	MemSet(econtext->ecxt_values, 0, sizeof(Datum) * length(node->aggs));
-	MemSet(econtext->ecxt_nulls, 0, sizeof(char) * length(node->aggs));
+	aggstate->agg_done = false;
+	MemSet(econtext->ecxt_values, 0, sizeof(Datum) * length(aggstate->aggs));
+	MemSet(econtext->ecxt_nulls, 0, sizeof(char) * length(aggstate->aggs));
 
 	/*
 	 * if chgParam of subnode is not null then plan will be re-scanned by