Re: vacuum, performance, and MVCC - Mailing list pgsql-hackers

From Jonah H. Harris
Subject Re: vacuum, performance, and MVCC
Date
Msg-id 36e682920606220720k132009ap81c06e41b28a8217@mail.gmail.com
Whole thread Raw
In response to Re: vacuum, performance, and MVCC  (Alvaro Herrera <alvherre@commandprompt.com>)
Responses Re: vacuum, performance, and MVCC  (Hannu Krosing <hannu@skype.net>)
List pgsql-hackers
On 6/22/06, Alvaro Herrera <alvherre@commandprompt.com> wrote:
> > Hmm, OK, then the problem is more serious than I suspected.
> > This means that every index on a row has to be updated on every
> > transaction that modifies that row. Is that correct?
>
> Add an index entry, yes.

Again, this is a case for update-in-place.  No need to write an extra
index entry and incur the WAL associated with it.  Imagine a table
with 3 indexes on it... I would estimate that we perform at least 3 to
6 times more overhead than any commercial database on such an update.

> > There has to be a more linear way of handling this scenario.
>
> So vacuum the table often.

It's easy to say VACUUM often... but I'd bet that vacuuming is going
to lessen the throughput in his tests even more; no matter how it's
tuned.

-- 
Jonah H. Harris, Software Architect | phone: 732.331.1300
EnterpriseDB Corporation            | fax: 732.331.1301
33 Wood Ave S, 2nd Floor            | jharris@enterprisedb.com
Iselin, New Jersey 08830            | http://www.enterprisedb.com/


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