On Sat, Dec 13, 2014 at 9:36 AM, Michael Paquier <michael.paqu...@gmail.com> wrote: > Something to be aware of btw is that this patch introduces an > additional 8 bytes per block image in WAL as it contains additional > information to control the compression. In this case this is the > uint16 compress_len present in XLogRecordBlockImageHeader. In the case > of the measurements done, knowing that 63638 FPWs have been written, > there is a difference of a bit less than 500k in WAL between HEAD and > "FPW off" in favor of HEAD. The gain with compression is welcome, > still for the default there is a small price to track down if a block > is compressed or not. This patch still takes advantage of it by not > compressing the hole present in page and reducing CPU work a bit.
That sounds like a pretty serious problem to me. -- 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
