From bb0aed591f1e8c9bee51360bf6cb77be8c6eb475 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 20 Feb 2005 22:02:19 +0000
Subject: [PATCH] Use SnapshotNow instead of SnapshotSelf for reading the
catalogs during flat-file writing. The only difference is that SnapshotSelf
would consider tuples of the 'current command' within the current transaction
as valid, where SnapshotNow wouldn't. We can eliminate the need for this
with one extra CommandCounterIncrement call before we start reading the
catalogs.
---
src/backend/utils/init/flatfiles.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/src/backend/utils/init/flatfiles.c b/src/backend/utils/init/flatfiles.c
index 0cbb878f9ff..8968d572c88 100644
--- a/src/backend/utils/init/flatfiles.c
+++ b/src/backend/utils/init/flatfiles.c
@@ -22,7 +22,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/backend/utils/init/flatfiles.c,v 1.2 2005/02/20 04:45:59 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/init/flatfiles.c,v 1.3 2005/02/20 22:02:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -235,11 +235,9 @@ write_database_file(Relation drel)
tempname)));
/*
- * Read pg_database and write the file. Note we use SnapshotSelf to
- * ensure we see all effects of current transaction. (Perhaps could
- * do a CommandCounterIncrement beforehand, instead?)
+ * Read pg_database and write the file.
*/
- scan = heap_beginscan(drel, SnapshotSelf, 0, NULL);
+ scan = heap_beginscan(drel, SnapshotNow, 0, NULL);
while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
{
Form_pg_database dbform = (Form_pg_database) GETSTRUCT(tuple);
@@ -349,11 +347,9 @@ write_group_file(Relation grel)
tempname)));
/*
- * Read pg_group and write the file. Note we use SnapshotSelf to
- * ensure we see all effects of current transaction. (Perhaps could
- * do a CommandCounterIncrement beforehand, instead?)
+ * Read pg_group and write the file.
*/
- scan = heap_beginscan(grel, SnapshotSelf, 0, NULL);
+ scan = heap_beginscan(grel, SnapshotNow, 0, NULL);
while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
{
Form_pg_group grpform = (Form_pg_group) GETSTRUCT(tuple);
@@ -491,11 +487,9 @@ write_user_file(Relation urel)
tempname)));
/*
- * Read pg_shadow and write the file. Note we use SnapshotSelf to
- * ensure we see all effects of current transaction. (Perhaps could
- * do a CommandCounterIncrement beforehand, instead?)
+ * Read pg_shadow and write the file.
*/
- scan = heap_beginscan(urel, SnapshotSelf, 0, NULL);
+ scan = heap_beginscan(urel, SnapshotNow, 0, NULL);
while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
{
Form_pg_shadow pwform = (Form_pg_shadow) GETSTRUCT(tuple);
@@ -713,6 +707,12 @@ AtEOXact_UpdateFlatFiles(bool isCommit)
return;
}
+ /*
+ * Advance command counter to be certain we see all effects of the
+ * current transaction.
+ */
+ CommandCounterIncrement();
+
/*
* We use ExclusiveLock to ensure that only one backend writes the
* flat file(s) at a time. That's sufficient because it's okay to
--
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