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Mark commit and abort WAL records with XLR_SPECIAL_REL_UPDATE.

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If a commit or abort record includes "dropped relfilenodes", then replaying
the record will remove data files. That is surely a "special rel update",
but the records were not marked as such. Fix that, teach pg_rewind to
expect and ignore them, and add a test case to cover it.

It's always been like this, but no backporting for fear of breaking
existing applications. If an application parsed the WAL but was not
handling commit/abort records, it would stop working. That might be a good
thing if it really needed to handle the dropped rels, but it will be caught
when the application is updated to work with PostgreSQL v14 anyway.

Discussion: https://www.postgresql.org/message-id/07b33e2c-46a6-86a1-5f9e-a7da73fddb95%40iki.fi
Reviewed-by: Amit Kapila, Michael Paquier
This commit is contained in:
Heikki Linnakangas 2020-08-17 10:52:58 +03:00
parent 3941eb6341
commit a28d731a11
3 changed files with 29 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/backend/access/transam/xact.c
View File

@ -5565,6 +5565,7 @@ XactLogCommitRecord(TimestampTz commit_time,
{
xl_xinfo.xinfo |= XACT_XINFO_HAS_RELFILENODES;
xl_relfilenodes.nrels = nrels;
info |= XLR_SPECIAL_REL_UPDATE;
}
if (nmsgs > 0)
@ -5697,6 +5698,7 @@ XactLogAbortRecord(TimestampTz abort_time,
{
xl_xinfo.xinfo |= XACT_XINFO_HAS_RELFILENODES;
xl_relfilenodes.nrels = nrels;
info |= XLR_SPECIAL_REL_UPDATE;
}
if (TransactionIdIsValid(twophase_xid))

13
src/bin/pg_rewind/parsexlog.c
View File

@ -14,6 +14,7 @@
#include <unistd.h>
#include "access/rmgr.h"
#include "access/xact.h"
#include "access/xlog_internal.h"
#include "access/xlogreader.h"
#include "catalog/pg_control.h"
@ -397,6 +398,18 @@ extractPageInfo(XLogReaderState *record)
* source system.
*/
}
else if (rmid == RM_XACT_ID &&
((rminfo & XLOG_XACT_OPMASK) == XLOG_XACT_COMMIT ||
(rminfo & XLOG_XACT_OPMASK) == XLOG_XACT_COMMIT_PREPARED ||
(rminfo & XLOG_XACT_OPMASK) == XLOG_XACT_ABORT ||
(rminfo & XLOG_XACT_OPMASK) == XLOG_XACT_ABORT_PREPARED))
{
/*
* These records can include "dropped rels". We can safely ignore
* them, we will see that they are missing and copy them from the
* source.
*/
}
else if (info & XLR_SPECIAL_REL_UPDATE)
{
/*

15
src/bin/pg_rewind/t/001_basic.pl
View File

@ -1,7 +1,7 @@
use strict;
use warnings;
use TestLib;
use Test::More tests => 20;
use Test::More tests => 23;
use FindBin;
use lib $FindBin::RealBin;
@ -29,6 +29,10 @@ sub run_test
primary_psql("CREATE TABLE tail_tbl (id integer, d text)");
primary_psql("INSERT INTO tail_tbl VALUES (0, 'in primary')");
# This test table is dropped in the old primary after promotion.
primary_psql("CREATE TABLE drop_tbl (d text)");
primary_psql("INSERT INTO drop_tbl VALUES ('in primary')");
primary_psql("CHECKPOINT");
RewindTest::create_standby($test_mode);
@ -66,6 +70,9 @@ sub run_test
primary_psql("DELETE FROM tail_tbl WHERE id > 10");
primary_psql("VACUUM tail_tbl");
# Drop drop_tbl. pg_rewind should copy it back.
primary_psql("DROP TABLE drop_tbl");
# Before running pg_rewind, do a couple of extra tests with several
# option combinations. As the code paths taken by those tests
# do not change for the "local" and "remote" modes, just run them
@ -154,6 +161,12 @@ in primary, before promotion
),
'tail-copy');
check_query(
'SELECT * FROM drop_tbl',
qq(in primary
),
'drop');
# Permissions on PGDATA should be default
SKIP:
{