From f04db8fee6508000d3fdbbcaf1577186959ac310 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Fri, 14 Aug 2020 11:36:18 +0300 Subject: [PATCH 2/2] Mark commit and abort WAL records with XLR_SPECIAL_REL_UPDATE. 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. 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 parser the WAL but is not handling commit/abort records, it would stop working. That might be a good thing if it would actually need to handle the dropped rels, but it will be caught when the application is updated to work with PostgreSQL v14 anyway. --- src/backend/access/transam/xact.c | 2 ++ src/bin/pg_rewind/parsexlog.c | 13 +++++++++++++ src/bin/pg_rewind/t/001_basic.pl | 15 ++++++++++++++- 3 files changed, 29 insertions(+), 1 deletion(-) diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index 7ccb7d68ed9..af6afcebb13 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -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)) diff --git a/src/bin/pg_rewind/parsexlog.c b/src/bin/pg_rewind/parsexlog.c index 2325fb5d302..2229c86f9af 100644 --- a/src/bin/pg_rewind/parsexlog.c +++ b/src/bin/pg_rewind/parsexlog.c @@ -14,6 +14,7 @@ #include #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) { /* diff --git a/src/bin/pg_rewind/t/001_basic.pl b/src/bin/pg_rewind/t/001_basic.pl index fb4a0acd965..ba528e262f3 100644 --- a/src/bin/pg_rewind/t/001_basic.pl +++ b/src/bin/pg_rewind/t/001_basic.pl @@ -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: { -- 2.20.1