Fix incremental backup interaction with XLOG_DBASE_CREATE_FILE_COPY.

After XLOG_DBASE_CREATE_FILE_COPY, a correct incremental backup needs
to copy in full everything with the database and tablespace OID
mentioned in that record; but that record doesn't specifically mention
the blocks, or even the relfilenumbers, of the affected relations.
As a result, we were failing to copy data that we should have copied.

To fix, enter the DB OID and tablespace OID into the block reference
table with relfilenumber 0 and limit block 0; and treat that as a
limit block of 0 for every relfilenumber whose DB OID and tablespace
OID match.

Also, add a test case.

Patch by me, reviewed by Noah Misch.

Discussion: http://postgr.es/m/CA+Tgmob0xa=ByvGLMdAgkUZyVQE=r4nyYZ_VEa40FCfEDFnTKA@mail.gmail.com

diff --git a/src/backend/backup/basebackup_incremental.c b/src/backend/backup/basebackup_incremental.c
index 18c78adda26c53012a5d053ab69c7ae661577c31..a8f2e72e7b1e49dbc619a0538f0666dc277220ed 100644 (file)
--- a/src/backend/backup/basebackup_incremental.c
+++ b/src/backend/backup/basebackup_incremental.c
@@ -777,9 +777,25 @@ GetFileBackupMethod(IncrementalBackupInfo *ib, const char *path,
            return BACK_UP_FILE_FULLY;
    }
 
-   /* Look up the block reference table entry. */
+   /*
+    * Look up the special block reference table entry for the database as
+    * a whole.
+    */
    rlocator.spcOid = spcoid;
    rlocator.dbOid = dboid;
+   rlocator.relNumber = 0;
+   if (BlockRefTableGetEntry(ib->brtab, &rlocator, MAIN_FORKNUM,
+                             &limit_block) != NULL)
+   {
+       /*
+        * According to the WAL summary, this database OID/tablespace OID
+        * pairing has been created since the previous backup. So, everything
+        * in it must be backed up fully.
+        */
+       return BACK_UP_FILE_FULLY;
+   }
+
+   /* Look up the block reference table entry for this relfilenode. */
    rlocator.relNumber = relfilenumber;
    brtentry = BlockRefTableGetEntry(ib->brtab, &rlocator, forknum,
                                     &limit_block);

diff --git a/src/backend/postmaster/walsummarizer.c b/src/backend/postmaster/walsummarizer.c
index 54fab16c37875d2e1d2170162aef7bdca0db5ec7..5a8006ea4c74a5891741ff97272eea14ea6f3577 100644 (file)
--- a/src/backend/postmaster/walsummarizer.c
+++ b/src/backend/postmaster/walsummarizer.c
@@ -29,6 +29,7 @@
 #include "access/xlogutils.h"
 #include "backup/walsummary.h"
 #include "catalog/storage_xlog.h"
+#include "commands/dbcommands_xlog.h"
 #include "common/blkreftable.h"
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
@@ -146,6 +147,8 @@ static void HandleWalSummarizerInterrupts(void);
 static XLogRecPtr SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn,
                               bool exact, XLogRecPtr switch_lsn,
                               XLogRecPtr maximum_lsn);
+static void SummarizeDbaseRecord(XLogReaderState *xlogreader,
+                                BlockRefTable *brtab);
 static void SummarizeSmgrRecord(XLogReaderState *xlogreader,
                                BlockRefTable *brtab);
 static void SummarizeXactRecord(XLogReaderState *xlogreader,
@@ -961,6 +964,9 @@ SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn, bool exact,
        /* Special handling for particular types of WAL records. */
        switch (XLogRecGetRmid(xlogreader))
        {
+           case RM_DBASE_ID:
+               SummarizeDbaseRecord(xlogreader, brtab);
+               break;
            case RM_SMGR_ID:
                SummarizeSmgrRecord(xlogreader, brtab);
                break;
@@ -1074,6 +1080,75 @@ SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn, bool exact,
    return summary_end_lsn;
 }
 
+/*
+ * Special handling for WAL records with RM_DBASE_ID.
+ */
+static void
+SummarizeDbaseRecord(XLogReaderState *xlogreader, BlockRefTable *brtab)
+{
+   uint8       info = XLogRecGetInfo(xlogreader) & ~XLR_INFO_MASK;
+
+   /*
+    * We use relfilenode zero for a given database OID and tablespace OID
+    * to indicate that all relations with that pair of IDs have been
+    * recreated if they exist at all. Effectively, we're setting a limit
+    * block of 0 for all such relfilenodes.
+    *
+    * Technically, this special handling is only needed in the case of
+    * XLOG_DBASE_CREATE_FILE_COPY, because that can create a whole bunch
+    * of relation files in a directory without logging anything
+    * specific to each one. If we didn't mark the whole DB OID/TS OID
+    * combination in some way, then a tablespace that was dropped after
+    * the reference backup and recreated using the FILE_COPY method prior
+    * to the incremental backup would look just like one that was never
+    * touched at all, which would be catastrophic.
+    *
+    * But it seems best to adopt this treatment for all records that drop
+    * or create a DB OID/TS OID combination. That's similar to how we
+    * treat the limit block for individual relations, and it's an extra
+    * layer of safety here. We can never lose data by marking more stuff
+    * as needing to be backed up in full.
+    */
+   if (info == XLOG_DBASE_CREATE_FILE_COPY)
+   {
+       xl_dbase_create_file_copy_rec *xlrec;
+       RelFileLocator rlocator;
+
+       xlrec =
+           (xl_dbase_create_file_copy_rec *) XLogRecGetData(xlogreader);
+       rlocator.spcOid = xlrec->tablespace_id;
+       rlocator.dbOid = xlrec->db_id;
+       rlocator.relNumber = 0;
+       BlockRefTableSetLimitBlock(brtab, &rlocator, MAIN_FORKNUM, 0);
+   }
+   else if (info == XLOG_DBASE_CREATE_WAL_LOG)
+   {
+       xl_dbase_create_wal_log_rec *xlrec;
+       RelFileLocator rlocator;
+
+       xlrec = (xl_dbase_create_wal_log_rec *) XLogRecGetData(xlogreader);
+       rlocator.spcOid = xlrec->tablespace_id;
+       rlocator.dbOid = xlrec->db_id;
+       rlocator.relNumber = 0;
+       BlockRefTableSetLimitBlock(brtab, &rlocator, MAIN_FORKNUM, 0);
+   }
+   else if (info == XLOG_DBASE_DROP)
+   {
+       xl_dbase_drop_rec *xlrec;
+       RelFileLocator rlocator;
+       int     i;
+
+       xlrec = (xl_dbase_drop_rec *) XLogRecGetData(xlogreader);
+       rlocator.dbOid = xlrec->db_id;
+       rlocator.relNumber = 0;
+       for (i = 0; i < xlrec->ntablespaces; ++i)
+       {
+           rlocator.spcOid = xlrec->tablespace_ids[i];
+           BlockRefTableSetLimitBlock(brtab, &rlocator, MAIN_FORKNUM, 0);
+       }
+   }
+}
+
 /*
  * Special handling for WAL records with RM_SMGR_ID.
  */

diff --git a/src/bin/pg_combinebackup/meson.build b/src/bin/pg_combinebackup/meson.build
index 30dbbaa6cfac6ad56a77593f2c9997e4f7f0efc2..1d4b9c218fdbe87dba7e2932c8b107b54f50d405 100644 (file)
--- a/src/bin/pg_combinebackup/meson.build
+++ b/src/bin/pg_combinebackup/meson.build
@@ -33,6 +33,7 @@ tests += {
       't/003_timeline.pl',
       't/004_manifest.pl',
       't/005_integrity.pl',
+      't/006_db_file_copy.pl',
     ],
   }
 }

diff --git a/src/bin/pg_combinebackup/t/006_db_file_copy.pl b/src/bin/pg_combinebackup/t/006_db_file_copy.pl
new file mode 100644 (file)
index 0000000..24f5544
--- /dev/null
+++ b/src/bin/pg_combinebackup/t/006_db_file_copy.pl
@@ -0,0 +1,58 @@
+# Copyright (c) 2021-2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+use File::Compare;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+# Set up a new database instance.
+my $primary = PostgreSQL::Test::Cluster->new('primary');
+$primary->init(has_archiving => 1, allows_streaming => 1);
+$primary->append_conf('postgresql.conf', 'summarize_wal = on');
+$primary->start;
+
+# Initial setup.
+$primary->safe_psql('postgres', <
+CREATE DATABASE lakh OID = 100000 STRATEGY = FILE_COPY
+EOM
+$primary->safe_psql('lakh', <
+CREATE TABLE t1 (a int)
+EOM
+
+# Take a full backup.
+my $backup1path = $primary->backup_dir . '/backup1';
+$primary->command_ok(
+   [ 'pg_basebackup', '-D', $backup1path, '--no-sync', '-cfast' ],
+   "full backup");
+
+# Now make some database changes.
+$primary->safe_psql('postgres', <
+DROP DATABASE lakh;
+CREATE DATABASE lakh OID = 100000 STRATEGY = FILE_COPY
+EOM
+
+# Take an incremental backup.
+my $backup2path = $primary->backup_dir . '/backup2';
+$primary->command_ok(
+   [ 'pg_basebackup', '-D', $backup2path, '--no-sync', '-cfast',
+     '--incremental', $backup1path . '/backup_manifest' ],
+   "incremental backup");
+
+# Recover the incremental backup.
+my $restore = PostgreSQL::Test::Cluster->new('restore');
+$restore->init_from_backup($primary, 'backup2',
+                          combine_with_prior => [ 'backup1' ]);
+$restore->start();
+
+# Query the DB.
+my $stdout;
+my $stderr;
+$restore->psql('lakh', 'SELECT * FROM t1',
+              stdout => \$stdout, stderr => \$stderr);
+is($stdout, '', 'SELECT * FROM t1: no stdout');
+like($stderr, qr/relation "t1" does not exist/,
+    'SELECT * FROM t1: stderr missing table');
+
+done_testing();




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