On Tue, Sep 27, 2011 at 7:28 AM, Florian Pflug <f...@phlo.org> wrote: > On Sep26, 2011, at 22:39 , Tom Lane wrote: >> It might be worthwhile to invoke XLogCheckInvalidPages() as soon as >> we (think we) have reached consistency, rather than leaving it to be >> done only when we exit recovery mode. > > I believe we also need to prevent the creation of restart points before > we've reached consistency. If we're starting from an online backup, > and a checkpoint occurred between pg_start_backup() and pg_stop_backup(), > we currently create a restart point upon replaying that checkpoint's > xlog record. At that point, however, unresolved page references are > not an error, since a truncation that happened after the checkpoint > (but before pg_stop_backup()) might or might not be reflected in the > online backup.
Preventing the creation of restartpoints before reaching consistent point sounds fragile to the case where the backup takes very long time. It might also take very long time to reach consistent point when replaying from that backup. Which prevents also the removal of WAL files (e.g., streamed from the master server) for a long time, and then might cause disk full failure. ISTM that writing an invalid-page table to the disk for every restartpoints is better approach. If an invalid-page table is never updated after we've reached consistency point, we probably should make restartpoints write that table only after that point. And, if a reference to an invalid page is found after the consistent point, we should emit error and cancel a recovery. Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
