From 4e7d10c7cd2503193dc13a701ffd740a5741d5eb Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 24 Mar 2006 23:02:17 +0000
Subject: [PATCH] Comments in IndexBuildHeapScan describe the indexing of
recently-dead tuples as needed "to keep VACUUM from complaining", but
actually there is a more compelling reason to do it: failure to do so
violates MVCC semantics. This is because a pre-existing serializable
transaction might try to use the index after we finish (re)building it, and
it might fail to find tuples it should be able to see. We got this mostly
right, but not in the case of partial indexes: the code mistakenly discarded
recently-dead tuples for partial indexes. Fix that, and adjust the comments.
---
src/backend/catalog/index.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index ca057c7f2fa..1a5c3b3c3bd 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.263 2006/03/05 15:58:22 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.264 2006/03/24 23:02:17 tgl Exp $
*
*
* INTERFACE ROUTINES
@@ -1473,7 +1473,9 @@ IndexBuildHeapScan(Relation heapRelation,
/*
* If tuple is recently deleted then we must index it
- * anyway to keep VACUUM from complaining.
+ * anyway to preserve MVCC semantics. (Pre-existing
+ * transactions could try to use the index after we
+ * finish building it, and may need to see such tuples.)
*/
indexIt = true;
tupleIsAlive = false;
@@ -1541,13 +1543,10 @@ IndexBuildHeapScan(Relation heapRelation,
/*
* In a partial index, discard tuples that don't satisfy the
- * predicate. We can also discard recently-dead tuples, since VACUUM
- * doesn't complain about tuple count mismatch for partial indexes.
+ * predicate.
*/
if (predicate != NIL)
{
- if (!tupleIsAlive)
- continue;
if (!ExecQual(predicate, econtext, false))
continue;
}
--
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