On Wed, Aug 17, 2011 at 6:19 AM, Fujii Masao <masao.fu...@gmail.com> wrote: > 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.
Seems like something we could add to XLOG_PARAMETER_CHANGE fairly easily. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
