From: | Chris Browne <cbbrowne(at)acm(dot)org> |
---|---|
To: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: vacuum, performance, and MVCC |
Date: | 2006-06-22 16:08:53 |
Message-ID: | 604pydxje2.fsf@dba2.int.libertyrms.com |
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Lists: | pgsql-hackers |
nagy(at)ecircle-ag(dot)com (Csaba Nagy) writes:
>> > [...]
>> > There has to be a more linear way of handling this scenario.
>>
>> So vacuum the table often.
>
> Good advice, except if the table is huge :-)
... Then the table shouldn't be designed to be huge. That represents
a design error.
> Here we have for example some tables which are frequently updated but
> contain >100 million rows. Vacuuming that takes hours. And the dead row
> candidates are the ones which are updated again and again and looked up
> frequently...
This demonstrates that "archival" material and "active" data should be
kept separately.
They have different access patterns; kludging them into the same table
turns out badly.
> A good solution would be a new type of vacuum which does not need to
> do a full table scan but can clean the pending dead rows without
> that... I guess then I could vacuum really frequently those tables.
That's yet another feature that's on the ToDo list; the "Vacuum Space
Map."
The notion is to have lists of recently modified pages, and to
restrict VACUUM to those pages. (Probably a special version of
VACUUM...)
--
output = reverse("moc.enworbbc" "@" "enworbbc")
http://www.ntlug.org/~cbbrowne/lisp.html
"As I've gained more experience with Perl it strikes me that it
resembles Lisp in many ways, albeit Lisp as channeled by an awk script
on acid." -- Tim Moore (on comp.lang.lisp)
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