Rewrite of planner statistics-gathering code. ANALYZE is now available as

a separate statement (though it can still be invoked as part of VACUUM, too).
pg_statistic redesigned to be more flexible about what statistics are
stored.  ANALYZE now collects a list of several of the most common values,
not just one, plus a histogram (not just the min and max values).  Random
sampling is used to make the process reasonably fast even on very large
tables.  The number of values and histogram bins collected is now
user-settable via an ALTER TABLE command.

There is more still to do; the new stats are not being used everywhere
they could be in the planner.  But the remaining changes for this project
should be localized, and the behavior is already better than before.

A not-very-related change is that sorting now makes use of btree comparison
routines if it can find one, rather than invoking '<' twice.

1 files changed, 35 insertions, 44 deletions

diff --git a/src/backend/executor/nodeSort.c b/src/backend/executor/nodeSort.c
index 12c6f82a8b2..e0543a28109 100644
--- a/src/backend/executor/nodeSort.c
+++ b/src/backend/executor/nodeSort.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeSort.c,v 1.32 2001/03/22 06:16:13 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeSort.c,v 1.33 2001/05/07 00:43:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -20,24 +20,24 @@
 #include "utils/tuplesort.h"
 
 /* ----------------------------------------------------------------
- *		FormSortKeys(node)
+ *		ExtractSortKeys
  *
- *		Forms the structure containing information used to sort the relation.
+ *		Extract the sorting key information from the plan node.
  *
- *		Returns an array of ScanKeyData.
+ *		Returns two palloc'd arrays, one of sort operator OIDs and
+ *		one of attribute numbers.
  * ----------------------------------------------------------------
  */
-static ScanKey
-FormSortKeys(Sort *sortnode)
+static void
+ExtractSortKeys(Sort *sortnode,
+				Oid **sortOperators,
+				AttrNumber **attNums)
 {
-	ScanKey		sortkeys;
 	List	   *targetList;
-	List	   *tl;
 	int			keycount;
-	Resdom	   *resdom;
-	AttrNumber	resno;
-	Index		reskey;
-	Oid			reskeyop;
+	Oid		   *sortOps;
+	AttrNumber *attNos;
+	List	   *tl;
 
 	/*
 	 * get information from the node
@@ -46,36 +46,33 @@ FormSortKeys(Sort *sortnode)
 	keycount = sortnode->keycount;
 
 	/*
-	 * first allocate space for scan keys
+	 * first allocate space for results
 	 */
 	if (keycount <= 0)
-		elog(ERROR, "FormSortKeys: keycount <= 0");
-	sortkeys = (ScanKey) palloc(keycount * sizeof(ScanKeyData));
-	MemSet((char *) sortkeys, 0, keycount * sizeof(ScanKeyData));
+		elog(ERROR, "ExtractSortKeys: keycount <= 0");
+	sortOps = (Oid *) palloc(keycount * sizeof(Oid));
+	MemSet(sortOps, 0, keycount * sizeof(Oid));
+	*sortOperators = sortOps;
+	attNos = (AttrNumber *) palloc(keycount * sizeof(AttrNumber));
+	MemSet(attNos, 0, keycount * sizeof(AttrNumber));
+	*attNums = attNos;
 
 	/*
-	 * form each scan key from the resdom info in the target list
+	 * extract info from the resdom nodes in the target list
 	 */
 	foreach(tl, targetList)
 	{
 		TargetEntry *target = (TargetEntry *) lfirst(tl);
-
-		resdom = target->resdom;
-		resno = resdom->resno;
-		reskey = resdom->reskey;
-		reskeyop = resdom->reskeyop;
+		Resdom	   *resdom = target->resdom;
+		Index		reskey = resdom->reskey;
 
 		if (reskey > 0)			/* ignore TLEs that are not sort keys */
 		{
-			ScanKeyEntryInitialize(&sortkeys[reskey - 1],
-								   0x0,
-								   resno,
-								   (RegProcedure) reskeyop,
-								   (Datum) 0);
+			Assert(reskey <= keycount);
+			sortOps[reskey - 1] = resdom->reskeyop;
+			attNos[reskey - 1] = resdom->resno;
 		}
 	}
-
-	return sortkeys;
 }
 
 /* ----------------------------------------------------------------
@@ -124,8 +121,8 @@ ExecSort(Sort *node)
 	{
 		Plan	   *outerNode;
 		TupleDesc	tupDesc;
-		int			keycount;
-		ScanKey		sortkeys;
+		Oid		   *sortOperators;
+		AttrNumber *attNums;
 
 		SO1_printf("ExecSort: %s\n",
 				   "sorting subplan");
@@ -145,14 +142,17 @@ ExecSort(Sort *node)
 
 		outerNode = outerPlan((Plan *) node);
 		tupDesc = ExecGetTupType(outerNode);
-		keycount = node->keycount;
-		sortkeys = (ScanKey) sortstate->sort_Keys;
 
-		tuplesortstate = tuplesort_begin_heap(tupDesc, keycount, sortkeys,
-											  true /* randomAccess */ );
+		ExtractSortKeys(node, &sortOperators, &attNums);
 
+		tuplesortstate = tuplesort_begin_heap(tupDesc, node->keycount,
+											  sortOperators, attNums,
+											  true /* randomAccess */ );
 		sortstate->tuplesortstate = (void *) tuplesortstate;
 
+		pfree(sortOperators);
+		pfree(attNums);
+
 		/*
 		 * Scan the subplan and feed all the tuples to tuplesort.
 		 */
@@ -230,7 +230,6 @@ ExecInitSort(Sort *node, EState *estate, Plan *parent)
 	 */
 	sortstate = makeNode(SortState);
 	sortstate->sort_Done = false;
-	sortstate->sort_Keys = NULL;
 	sortstate->tuplesortstate = NULL;
 
 	node->sortstate = sortstate;
@@ -259,11 +258,6 @@ ExecInitSort(Sort *node, EState *estate, Plan *parent)
 	ExecInitNode(outerPlan, estate, (Plan *) node);
 
 	/*
-	 * initialize sortstate information
-	 */
-	sortstate->sort_Keys = FormSortKeys(node);
-
-	/*
 	 * initialize tuple type.  no need to initialize projection info
 	 * because this node doesn't do projections.
 	 */
@@ -321,9 +315,6 @@ ExecEndSort(Sort *node)
 		tuplesort_end((Tuplesortstate *) sortstate->tuplesortstate);
 	sortstate->tuplesortstate = NULL;
 
-	if (sortstate->sort_Keys != NULL)
-		pfree(sortstate->sort_Keys);
-
 	pfree(sortstate);
 	node->sortstate = NULL;