On Wed, Feb 5, 2014 at 8:50 PM, Heikki Linnakangas <hlinnakan...@vmware.com> wrote: > On 02/05/2014 04:48 PM, Amit Kapila wrote: >> >> I have done one test where there is a large suffix match, but >> not large enough that it can compress more than 75% of string, >> the CPU overhead with wal-update-prefix-suffix-encode-1.patch is >> not much, but there is no I/O reduction as well. > > > Hmm, it's supposed to compress if you save at least 25%, not 75%. Apparently > I got that backwards in the patch...
Okay I think that is right, may be I can change the that check to see the difference, but in general isn't it going to loose compression in much more cases like if there is less than 25% match in prefix/suffix, but more than 50% match in between the string. While debugging, I noticed that it compresses less than history table approach for general cases when internally update is done like for Truncate table. With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers