From 7c8beefd5eaca39a6950a9523cf886950177cbef Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 26 May 1999 22:57:39 +0000
Subject: [PATCH] Patch from Andreas: when CREATE TABLE is followed by CREATE
INDEX before any tuples are loaded, preserve the default '1000 tuples' table
size estimate.
---
src/backend/catalog/heap.c | 11 +++---
src/backend/catalog/index.c | 67 +++++++++++++++++++++++--------------
2 files changed, 47 insertions(+), 31 deletions(-)
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index 89e45fb2bfc..1898f8f3087 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.85 1999/05/25 16:08:03 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.86 1999/05/26 22:57:39 tgl Exp $
*
*
* INTERFACE ROUTINES
@@ -674,11 +674,10 @@ AddNewRelationTuple(Relation pg_class_desc,
* enough to discourage the optimizer from using nested-loop plans.
* With this hack, nested-loop plans will be preferred only after
* the table has been proven to be small by VACUUM or CREATE INDEX.
- * (NOTE: if user does CREATE TABLE, then CREATE INDEX, then loads
- * the table, he still loses until he vacuums, because CREATE INDEX
- * will set reltuples to zero. Can't win 'em all. Maintaining the
- * stats on-the-fly would solve the problem, but the overhead of that
- * would likely cost more than it'd save.)
+ * Maintaining the stats on-the-fly would solve the problem more cleanly,
+ * but the overhead of that would likely cost more than it'd save.
+ * (NOTE: CREATE INDEX inserts the same bogus estimates if it finds the
+ * relation has 0 rows and pages. See index.c.)
* ----------------
*/
new_rel_reltup->relpages = 10; /* bogus estimates */
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 93f34ce0749..0c8e9d77b78 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/catalog/index.c,v 1.75 1999/05/25 16:08:06 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/catalog/index.c,v 1.76 1999/05/26 22:57:39 tgl Exp $
*
*
* INTERFACE ROUTINES
@@ -1291,7 +1291,6 @@ UpdateStats(Oid relid, long reltuples, bool hasindex)
if (!RelationIsValid(pg_class))
elog(ERROR, "UpdateStats: could not open RELATION relation");
-
if (!IsBootstrapProcessingMode())
{
tuple = SearchSysCacheTupleCopy(RELOID,
@@ -1320,34 +1319,48 @@ UpdateStats(Oid relid, long reltuples, bool hasindex)
}
/* ----------------
- * update statistics
+ * Figure values to insert.
+ *
+ * If we found zero tuples in the scan, do NOT believe it; instead put
+ * a bogus estimate into the statistics fields. Otherwise, the common
+ * pattern "CREATE TABLE; CREATE INDEX; insert data" leaves the table
+ * with zero size statistics until a VACUUM is done. The optimizer will
+ * generate very bad plans if the stats claim the table is empty when
+ * it is actually sizable. See also CREATE TABLE in heap.c.
* ----------------
*/
relpages = RelationGetNumberOfBlocks(whichRel);
+ if (reltuples == 0)
+ {
+ if (relpages == 0)
+ {
+ /* Bogus defaults for a virgin table, same as heap.c */
+ reltuples = 1000;
+ relpages = 10;
+ }
+ else if (whichRel->rd_rel->relkind == RELKIND_INDEX && relpages <= 2)
+ {
+ /* Empty index, leave bogus defaults in place */
+ reltuples = 1000;
+ }
+ else
+ reltuples = relpages * NTUPLES_PER_PAGE(whichRel->rd_rel->relnatts);
+ }
+
/*
* We shouldn't have to do this, but we do... Modify the reldesc in
* place with the new values so that the cache contains the latest
* copy.
*/
-
whichRel->rd_rel->relhasindex = hasindex;
whichRel->rd_rel->relpages = relpages;
whichRel->rd_rel->reltuples = reltuples;
- for (i = 0; i < Natts_pg_class; i++)
- {
- nulls[i] = heap_attisnull(tuple, i + 1) ? 'n' : ' ';
- replace[i] = ' ';
- values[i] = (Datum) NULL;
- }
-
- /*
- * If reltuples wasn't supplied take an educated guess.
+ /* ----------------
+ * Update statistics in pg_class.
+ * ----------------
*/
- if (reltuples == 0)
- reltuples = relpages * NTUPLES_PER_PAGE(whichRel->rd_rel->relnatts);
-
if (IsBootstrapProcessingMode())
{
@@ -1363,7 +1376,15 @@ UpdateStats(Oid relid, long reltuples, bool hasindex)
}
else
{
- /* during normal processing, work harder */
+ /* During normal processing, must work harder. */
+
+ for (i = 0; i < Natts_pg_class; i++)
+ {
+ nulls[i] = heap_attisnull(tuple, i + 1) ? 'n' : ' ';
+ replace[i] = ' ';
+ values[i] = (Datum) NULL;
+ }
+
replace[Anum_pg_class_relpages - 1] = 'r';
values[Anum_pg_class_relpages - 1] = (Datum) relpages;
replace[Anum_pg_class_reltuples - 1] = 'r';
@@ -1438,12 +1459,10 @@ DefaultBuild(Relation heapRelation,
char *nullv;
long reltuples,
indtuples;
-
#ifndef OMIT_PARTIAL_INDEX
ExprContext *econtext;
TupleTable tupleTable;
TupleTableSlot *slot;
-
#endif
Node *predicate;
Node *oldPred;
@@ -1524,13 +1543,13 @@ DefaultBuild(Relation heapRelation,
{
reltuples++;
+#ifndef OMIT_PARTIAL_INDEX
/*
* If oldPred != NULL, this is an EXTEND INDEX command, so skip
* this tuple if it was already in the existing partial index
*/
if (oldPred != NULL)
{
-#ifndef OMIT_PARTIAL_INDEX
/* SetSlotContents(slot, heapTuple); */
slot->val = heapTuple;
if (ExecQual((List *) oldPred, econtext) == true)
@@ -1538,7 +1557,6 @@ DefaultBuild(Relation heapRelation,
indtuples++;
continue;
}
-#endif /* OMIT_PARTIAL_INDEX */
}
/*
@@ -1547,13 +1565,12 @@ DefaultBuild(Relation heapRelation,
*/
if (predicate != NULL)
{
-#ifndef OMIT_PARTIAL_INDEX
/* SetSlotContents(slot, heapTuple); */
slot->val = heapTuple;
if (ExecQual((List *) predicate, econtext) == false)
continue;
-#endif /* OMIT_PARTIAL_INDEX */
}
+#endif /* OMIT_PARTIAL_INDEX */
indtuples++;
@@ -1586,12 +1603,12 @@ DefaultBuild(Relation heapRelation,
heap_endscan(scan);
+#ifndef OMIT_PARTIAL_INDEX
if (predicate != NULL || oldPred != NULL)
{
-#ifndef OMIT_PARTIAL_INDEX
ExecDestroyTupleTable(tupleTable, false);
-#endif /* OMIT_PARTIAL_INDEX */
}
+#endif /* OMIT_PARTIAL_INDEX */
pfree(nullv);
pfree(datum);
--
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