I'm looking to implement the following functions for Hot Standby, to allow those with administrative tools or management applications to have more control during recovery. Please let me know if other functions are required. What else do we need? * pg_is_in_recovery() returns bool (true if in recovery, false if not) * pg_last_recovered_xact_xid() Will throw an ERROR if *not* executed in recovery mode. returns bigint * pg_last_completed_xact_xid() Will throw an ERROR *if* executed in recovery mode. returns bigint (together allows easy arithmetic on xid difference between master and slave). * pg_last_recovered_xact_timestamp() returns timestamp with timezone (allows easy arithmetic with now() to allow derivation of replication delay etc) * pg_freeze_recovery() - freezes recovery after the current record has been applied. The server is still up and queries can happen, but no WAL replay will occur. This is a temporary state change and we keep no record of this, other than making a server log entry. If the server is shutdown or crashes, it will unfreeze itself automatically. Has no effect on master. Will throw an ERROR if not executed in recovery mode. Superusers only. returns text (XLogRecPtr of freeze point) * pg_unfreeze_recovery() - unfreezes recovery. Recovery will begin again at exactly the point recovery was frozen at. Will throw an ERROR is not executed in recovery mode. Superusers only. returns bool (true if unfroze, false if was not frozen when called) * pg_end_recovery() - Will force recovery to end at current location. Recovery mode cannot be easily re-entered, so there is no "restart" function. Will throw an ERROR is not executed in recovery mode. Superusers only. returns text (XLogRecPtr of freeze point) * pg_start_backup()/pg_stop_backup() could work during recovery, but the backup history file would need to be manually inserted into the archive once complete. Is that acceptable? (Note that we don't know where the archive is or how to access that; the information is all in recovery_command. We cannot assume that archive_command points to same archive. So making it happen automatically is too much work for this release, if ever.) If that seems useful, we could do this by avoiding any operation that changes WAL stream during recovery: no checkpoints, log switches etc.. pg_start_backup() would return XLogRecPtr of last restartpoint. pg_stop_backup() would return last known xlrec recovered (we won't keep track of this record by record). * pg_reload_conf() will not force re-read of recovery.conf since that may require extra work and doesn't seem that important, if we have the manual override mentioned above. All desirable? All possible? Any others? -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
