On 11/11/14, 2:03 PM, Alvaro Herrera wrote:
Jim Nasby wrote:
On 11/10/14, 7:40 AM, Alvaro Herrera wrote:
Ah, right. So AFAIK we don't need to keep anything older than
RecentXmin or something like that -- which is not too old. If I recall
correctly Josh Berkus was saying in a thread about pg_multixact that it
used about 128kB or so in <= 9.2 for his customers; that one was also
limited to RecentXmin AFAIR. I think a similar volume of commit_ts data
would be pretty acceptable. Moreso considering that it's turned off by
default.
FWIW, AFAICS MultiXacts are only truncated after a (auto)vacuum process is able
to advance datminmxid, which will (now) only happen when an entire relation has
been scanned (which should be infrequent).
I believe the low normal space usage is just an indication that most databases
don't use many MultiXacts.
That's in 9.3. Prior to that, they were truncated much more often.
Well, we're talking about a new feature, so I wasn't looking in back branches.
;P
Maybe you've not heard enough about this commit:
commit 0ac5ad5134f2769ccbaefec73844f8504c4d6182
Interestingly, git.postgresql.org hasn't either:
http://git.postgresql.org/gitweb/?p=postgresql.git&a=search&h=HEAD&st=commit&s=0ac5ad5134f2769ccbaefec73844f8504c4d6182
The commit is certainly there though...
decibel@decina:[15:12]~/pgsql/HEAD/src/backend (master=)$git log
0ac5ad5134f2769ccbaefec73844f8504c4d6182|head -n1
commit 0ac5ad5134f2769ccbaefec73844f8504c4d6182
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com
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