diff options
| author | Robert Haas | 2024-07-25 19:45:06 +0000 |
|---|---|---|
| committer | Robert Haas | 2024-07-25 19:45:06 +0000 |
| commit | 744ddc6c6a0fa5d4d6d0e187cadcc632daaefc0e (patch) | |
| tree | 007268af20c49363fd940f09cfa6b512431cdd42 | |
| parent | 580f8727ca93b7b9a2ce49746b9cdbcb0a2b4a7e (diff) | |
Document restrictions regarding incremental backups and standbys.
If you try to take an incremental backup on a standby and there hasn't
been much system activity, it might fail. Document why this happens.
Also add a hint to the error message you get, to make it more likely
that users will understand what has gone wrong.
Laurenz Albe and Robert Haas
Discussion: https://postgr.es/m/[email protected]
| -rw-r--r-- | doc/src/sgml/backup.sgml | 11 | ||||
| -rw-r--r-- | src/backend/backup/basebackup_incremental.c | 3 |
2 files changed, 13 insertions, 1 deletions
diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml index 91da3c26ba0..e4e4c56cf14 100644 --- a/doc/src/sgml/backup.sgml +++ b/doc/src/sgml/backup.sgml @@ -925,6 +925,17 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 && cp pg_wal/0 to manage. For a large database all of which is heavily modified, incremental backups won't be much smaller than full backups. </para> + + <para> + An incremental backup is only possible if replay would begin from a later + checkpoint than for the previous backup upon which it depends. If you + take the incremental backup on the primary, this condition is always + satisfied, because each backup triggers a new checkpoint. On a standby, + replay begins from the most recent restartpoint. Therefore, an + incremental backup of a standby server can fail if there has been very + little activity since the previous backup, since no new restartpoint might + have been created. + </para> </sect2> <sect2 id="backup-lowlevel-base-backup"> diff --git a/src/backend/backup/basebackup_incremental.c b/src/backend/backup/basebackup_incremental.c index 21087023973..a023e624403 100644 --- a/src/backend/backup/basebackup_incremental.c +++ b/src/backend/backup/basebackup_incremental.c @@ -441,7 +441,8 @@ PrepareForIncrementalBackup(IncrementalBackupInfo *ib, errmsg("manifest requires WAL from final timeline %u ending at %X/%X, but this backup starts at %X/%X", range->tli, LSN_FORMAT_ARGS(range->end_lsn), - LSN_FORMAT_ARGS(backup_state->startpoint)))); + LSN_FORMAT_ARGS(backup_state->startpoint)), + errhint("This can happen for incremental backups on a standby if there was little activity since the previous backup."))); } else { |