| From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
|---|---|
| To: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
| Cc: | Mikko Partio <mpartio(at)gmail(dot)com>, "ruben(at)rentalia(dot)com" <ruben(at)rentalia(dot)com>, Decibel! <decibel(at)decibel(dot)org>, db(at)zigo(dot)dhs(dot)org, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: [Again] Postgres performance problem |
| Date: | 2007-09-12 19:40:36 |
| Message-ID: | 20070912194036.GE2244@alvh.no-ip.org |
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| Lists: | pgsql-performance |
Scott Marlowe escribió:
> > Aren't you mixing up REINDEX and CLUSTER?
>
> I don't think so. reindex (which runs on tables and indexes, so the
> name is a bit confusing, I admit) basically was originally a "repair"
> operation that rewrote the whole relation and wasn't completely
> transaction safe (way back, 7.2 days or so I think). Due to the
> issues with vacuum full bloating indexes, and being slowly replaced by
> regular vacuum, reindex received some attention to make it transaction
> / crash safe and has kind of take the place of vacuum full in terms of
> "how to fix bloated objects".
Hmm, REINDEX does not rewrite tables. If there are dead tuples, they
will still be there after REINDEX.
> cluster, otoh, rewrites the table into index order.
... excluding dead tuples, and then rewrites all the indexes.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
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