On Thu, May 29, 2014 at 7:21 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > On 29 May 2014 01:07, Bruce Momjian <br...@momjian.us> wrote: >> On Wed, May 28, 2014 at 04:04:13PM +0100, Simon Riggs wrote: >>> On 28 May 2014 15:34, Fujii Masao <masao.fu...@gmail.com> wrote: >>> >>> >> Also, compress_backup_block GUC needs to be merged with full_page_writes. >>> > >>> > Basically I agree with you because I don't want to add new GUC very >>> > similar to >>> > the existing one. >>> > >>> > But could you imagine the case where full_page_writes = off. Even in this >>> > case, >>> > FPW is forcibly written only during base backup. Such FPW also should be >>> > compressed? Which compression algorithm should be used? If we want to >>> > choose the algorithm for such FPW, we would not be able to merge those two >>> > GUCs. IMO it's OK to always use the best compression algorithm for such >>> > FPW >>> > and merge them, though. >>> >>> I'd prefer a new name altogether >>> >>> torn_page_protection = 'full_page_writes' >>> torn_page_protection = 'compressed_full_page_writes' >>> torn_page_protection = 'none' >>> >>> this allows us to add new techniques later like >>> >>> torn_page_protection = 'background_FPWs' >>> >>> or >>> >>> torn_page_protection = 'double_buffering' >>> >>> when/if we add those new techniques >> >> Uh, how would that work if you want to compress the background_FPWs? >> Use compressed_background_FPWs? > > We've currently got 1 technique for torn page protection, soon to have > 2 and with a 3rd on the horizon and likely to receive effort in next > release. > > It seems sensible to have just one parameter to describe the various > techniques, as suggested. I'm suggesting that we plan for how things > will look when we have the 3rd one as well. > > Alternate suggestions welcome.
Is even compression of double buffer worthwhile? If yes, what about separating the GUC parameter into torn_page_protection and something like full_page_compression? ISTM that any combination of settings of those parameters can work. torn_page_protection = 'FPW', 'background FPW', 'none', 'double buffer' full_page_compression = 'no', 'pglz', 'lz4', 'snappy' Regards, -- Fujii Masao -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
