2011/8/17 Jun Ishiduka <ishizuka....@po.ntts.co.jp>: >> I see in xlog.h XLR_BKP_REMOVABLE, the comment above it says that this >> flag is used to indicate that the archiver can compress the full page >> blocks to non-full page blocks. I am not familiar with where in the code >> this actually happens but will this cause issues if the first standby is >> processing WAL files from the archive? > > I confirmed the flag in xlog.c, so I seemed to only insert it in > XLogInsert(). I consider whether it is available.
That flag is not available to check whether full-page writing was skipped or not. Because it's in full-page data, not non-full-page one. The straightforward approach to address the problem you raised is to log the change of full_page_writes on the master. Since such a WAL record is also replicated to the standby, the standby can know whether full_page_writes is enabled or not in the master, from the WAL record. If it's disabled, pg_start_backup() in the standby should emit an error and refuse standby-only backup. If the WAL record indicating that full_page_writes was disabled on the master arrives during standby-only backup, the standby should cancel the backup. 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
