From 1e9a6ba5e6984186dca7f5d827b9f92c9fe17e51 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 13 Oct 2005 00:06:46 +0000
Subject: [PATCH] Don't try to remove duplicate OR-subclauses in
create_bitmap_subplan and make_restrictinfo_from_bitmapqual. The likelihood
of finding duplicates seems much less than in the AND-subclause case, and the
cost much higher, because OR lists with hundreds or even thousands of
subclauses are not uncommon. Per discussion with Ilia Kantor and
andrew@supernews.
---
src/backend/optimizer/plan/createplan.c | 20 ++++++++++++--------
src/backend/optimizer/util/restrictinfo.c | 20 ++++++++++++--------
2 files changed, 24 insertions(+), 16 deletions(-)
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 8d1d7a2ecad..b7af04e1b9f 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.199 2005/10/06 16:01:54 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.200 2005/10/13 00:06:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1046,9 +1046,13 @@ create_bitmap_subplan(PlannerInfo *root, Path *bitmapqual,
ListCell *l;
/*
- * Here, we detect both obvious redundancies and qual-free subplans.
- * A qual-free subplan would cause us to generate "... OR true ..."
- * which we may as well reduce to just "true".
+ * Here, we only detect qual-free subplans. A qual-free subplan would
+ * cause us to generate "... OR true ..." which we may as well reduce
+ * to just "true". We do not try to eliminate redundant subclauses
+ * because (a) it's not as likely as in the AND case, and (b) we might
+ * well be working with hundreds or even thousands of OR conditions,
+ * perhaps from a long IN list. The performance of list_append_unique
+ * would be unacceptable.
*/
foreach(l, opath->bitmapquals)
{
@@ -1062,13 +1066,13 @@ create_bitmap_subplan(PlannerInfo *root, Path *bitmapqual,
if (subqual == NIL)
const_true_subqual = true;
else if (!const_true_subqual)
- subquals = list_append_unique(subquals,
- make_ands_explicit(subqual));
+ subquals = lappend(subquals,
+ make_ands_explicit(subqual));
if (subindexqual == NIL)
const_true_subindexqual = true;
else if (!const_true_subindexqual)
- subindexquals = list_append_unique(subindexquals,
- make_ands_explicit(subindexqual));
+ subindexquals = lappend(subindexquals,
+ make_ands_explicit(subindexqual));
}
plan = (Plan *) make_bitmap_or(subplans);
plan->startup_cost = opath->path.startup_cost;
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index deb16152fb8..47b90aef46a 100644
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.39 2005/07/28 20:26:21 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.40 2005/10/13 00:06:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -123,9 +123,13 @@ make_restrictinfo_from_bitmapqual(Path *bitmapqual,
List *withoutris = NIL;
/*
- * Here, we detect both obvious redundancies and qual-free subplans.
- * A qual-free subplan would cause us to generate "... OR true ..."
- * which we may as well reduce to just "true".
+ * Here, we only detect qual-free subplans. A qual-free subplan would
+ * cause us to generate "... OR true ..." which we may as well reduce
+ * to just "true". We do not try to eliminate redundant subclauses
+ * because (a) it's not as likely as in the AND case, and (b) we might
+ * well be working with hundreds or even thousands of OR conditions,
+ * perhaps from a long IN list. The performance of list_append_unique
+ * would be unacceptable.
*/
foreach(l, opath->bitmapquals)
{
@@ -144,12 +148,12 @@ make_restrictinfo_from_bitmapqual(Path *bitmapqual,
return NIL;
}
/* Create AND subclause with RestrictInfos */
- withris = list_append_unique(withris,
- make_ands_explicit(sublist));
+ withris = lappend(withris,
+ make_ands_explicit(sublist));
/* And one without */
sublist = get_actual_clauses(sublist);
- withoutris = list_append_unique(withoutris,
- make_ands_explicit(sublist));
+ withoutris = lappend(withoutris,
+ make_ands_explicit(sublist));
}
/*
--
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