Delete pg_statistics rows for a relation during heap_destroy_with_catalog.

By dropping stats rows here, we eliminate the need for VACUUM to do a
wholesale remove of stats rows.  Before, pg_statistics was wiped clean
at the start of VACUUM, ensuring poor planning results for any backends
running in parallel until VACUUM got around to rebuilding the stats for
the relations they are accessing.

src/backend/catalog/heap.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.110 1999/11/24 00:44:29 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.111 1999/11/28 02:03:04 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -44,6 +44,7 @@
 #include "catalog/pg_ipl.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_relcheck.h"
+#include "catalog/pg_statistic.h"
 #include "catalog/pg_type.h"
 #include "commands/comment.h"
 #include "commands/trigger.h"
@@ -82,6 +83,7 @@ static void StoreAttrDefault(Relation rel, AttrNumber attnum, char *adbin,
 static void StoreRelCheck(Relation rel, char *ccname, char *ccbin);
 static void StoreConstraints(Relation rel);
 static void RemoveConstraints(Relation rel);
+static void RemoveStatistics(Relation rel);
 
 
 /* ----------------------------------------------------------------
@@ -1232,7 +1234,7 @@ heap_truncate(char *relname)
 	/* Open relation for processing, and grab exclusive access on it. */
 
 	rel = heap_openr(relname, AccessExclusiveLock);
-	rid = rel->rd_id;
+	rid = RelationGetRelid(rel);
 
 	/* ----------------
 	 *	TRUNCATE TABLE within a transaction block is dangerous, because
@@ -1455,7 +1457,7 @@ heap_destroy_with_catalog(char *relname)
 	 * ----------------
 	 */
 	rel = heap_openr(relname, AccessExclusiveLock);
-	rid = rel->rd_id;
+	rid = RelationGetRelid(rel);
 
 	/* ----------------
 	 *	prevent deletion of system relations
@@ -1512,12 +1514,17 @@ heap_destroy_with_catalog(char *relname)
 	DeleteAttributeTuples(rel);
 
 	/* ----------------
-	 *      delete comments
-         * ----------------
-         */
-
+	 *	delete comments
+	 * ----------------
+	 */
 	DeleteComments(RelationGetRelid(rel));
 
+	/* ----------------
+	 *	delete statistics
+	 * ----------------
+	 */
+	RemoveStatistics(rel);
+
 	/* ----------------
 	 *	delete type tuple.	here we want to see the effects
 	 *	of the deletions we just did, so we use setheapoverride().
@@ -1731,7 +1738,7 @@ StoreAttrDefault(Relation rel, AttrNumber attnum, char *adbin,
 	rte->skipAcl = false;
 	adsrc = deparse_expression(expr, lcons(lcons(rte, NIL), NIL), false);
 
-	values[Anum_pg_attrdef_adrelid - 1] = rel->rd_id;
+	values[Anum_pg_attrdef_adrelid - 1] = RelationGetRelid(rel);
 	values[Anum_pg_attrdef_adnum - 1] = attnum;
 	values[Anum_pg_attrdef_adbin - 1] = PointerGetDatum(textin(adbin));
 	values[Anum_pg_attrdef_adsrc - 1] = PointerGetDatum(textin(adsrc));
@@ -1754,11 +1761,11 @@ StoreAttrDefault(Relation rel, AttrNumber attnum, char *adbin,
 
 	attrrel = heap_openr(AttributeRelationName, RowExclusiveLock);
 	atttup = SearchSysCacheTupleCopy(ATTNUM,
-									 ObjectIdGetDatum(rel->rd_id),
+									 ObjectIdGetDatum(RelationGetRelid(rel)),
 									 (Datum) attnum, 0, 0);
 	if (!HeapTupleIsValid(atttup))
 		elog(ERROR, "cache lookup of attribute %d in relation %u failed",
-			 attnum, rel->rd_id);
+			 attnum, RelationGetRelid(rel));
 	attStruct = (Form_pg_attribute) GETSTRUCT(atttup);
 	if (! attStruct->atthasdef)
 	{
@@ -1810,7 +1817,7 @@ StoreRelCheck(Relation rel, char *ccname, char *ccbin)
 	rte->skipAcl = false;
 	ccsrc = deparse_expression(expr, lcons(lcons(rte, NIL), NIL), false);
 
-	values[Anum_pg_relcheck_rcrelid - 1] = rel->rd_id;
+	values[Anum_pg_relcheck_rcrelid - 1] = RelationGetRelid(rel);
 	values[Anum_pg_relcheck_rcname - 1] = PointerGetDatum(namein(ccname));
 	values[Anum_pg_relcheck_rcbin - 1] = PointerGetDatum(textin(ccbin));
 	values[Anum_pg_relcheck_rcsrc - 1] = PointerGetDatum(textin(ccsrc));
@@ -2077,10 +2084,10 @@ AddRelationRawConstraints(Relation rel,
 	 */
 	relrel = heap_openr(RelationRelationName, RowExclusiveLock);
 	reltup = SearchSysCacheTupleCopy(RELOID,
-									 ObjectIdGetDatum(rel->rd_id),
+									 ObjectIdGetDatum(RelationGetRelid(rel)),
 									 0, 0, 0);
 	if (!HeapTupleIsValid(reltup))
-		elog(ERROR, "cache lookup of relation %u failed", rel->rd_id);
+		elog(ERROR, "cache lookup of relation %u failed", RelationGetRelid(rel));
 	relStruct = (Form_pg_class) GETSTRUCT(reltup);
 
 	relStruct->relchecks = numchecks;
@@ -2120,7 +2127,7 @@ RemoveAttrDefault(Relation rel)
 	adrel = heap_openr(AttrDefaultRelationName, RowExclusiveLock);
 
 	ScanKeyEntryInitialize(&key, 0, Anum_pg_attrdef_adrelid,
-						   F_OIDEQ, rel->rd_id);
+						   F_OIDEQ, RelationGetRelid(rel));
 
 	adscan = heap_beginscan(adrel, 0, SnapshotNow, 1, &key);
 
@@ -2142,7 +2149,7 @@ RemoveRelCheck(Relation rel)
 	rcrel = heap_openr(RelCheckRelationName, RowExclusiveLock);
 
 	ScanKeyEntryInitialize(&key, 0, Anum_pg_relcheck_rcrelid,
-						   F_OIDEQ, rel->rd_id);
+						   F_OIDEQ, RelationGetRelid(rel));
 
 	rcscan = heap_beginscan(rcrel, 0, SnapshotNow, 1, &key);
 
@@ -2167,3 +2174,25 @@ RemoveConstraints(Relation rel)
 	if (constr->num_check > 0)
 		RemoveRelCheck(rel);
 }
+
+static void
+RemoveStatistics(Relation rel)
+{
+	Relation	pgstatistic;
+	HeapScanDesc scan;
+	ScanKeyData key;
+	HeapTuple	tuple;
+
+	pgstatistic = heap_openr(StatisticRelationName, RowExclusiveLock);
+
+	ScanKeyEntryInitialize(&key, 0x0, Anum_pg_statistic_starelid,
+						   F_OIDEQ,
+						   ObjectIdGetDatum(RelationGetRelid(rel)));
+	scan = heap_beginscan(pgstatistic, false, SnapshotNow, 1, &key);
+
+	while (HeapTupleIsValid(tuple = heap_getnext(scan, 0)))
+		heap_delete(pgstatistic, &tuple->t_self, NULL);
+
+	heap_endscan(scan);
+	heap_close(pgstatistic, RowExclusiveLock);
+}