On 11/07/2014 04:43 PM, Alvaro Herrera wrote: > This says that the live multixact range goes from 123 million to 162 > million; roughly 40 million values. (The default value for > vacuum_multixact_freeze_table_age is 150 million, which is what > determines how many values are kept.) > > You gist.github paste tells us there are 4598 members files. Each file > has 32 pages, and each page hosts 2045 members; so there are 32 * 2045 * > 4598 members, or somewhat about 300 million. For 40 million > multixacts, this means there are about 7 members per multixact, in > average, which seems a reasonable number to me.
So the basic problem is that multixact files are just huge, with an average of 35 bytes per multixact? > If you want to have vacuum truncate pg_multixact more aggresively, you > need to decrease vacuum_multixact_freeze_table_age and > vacuum_multixact_freeze_min_age. If that's the case, then we need to set the defaults more aggressively. I suggest maybe 10 million. The alternative is allowing it to creep up to 150million, which would be 5GB. I don't see adding 5GB to user databases without warning them as good behavior. Of course, this will lead to LOTs of additional vacuuming ... -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
