| From: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> |
|---|---|
| To: | "Gauri Kanekar" <meetgaurikanekar(at)gmail(dot)com> |
| Cc: | "Andrew Sullivan" <ajs(at)commandprompt(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Replication Syatem |
| Date: | 2008-04-29 05:55:27 |
| Message-ID: | 2e78013d0804282255t48285141pf49d71bb63e8cf48@mail.gmail.com |
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| Lists: | pgsql-performance |
On Tue, Apr 29, 2008 at 11:16 AM, Gauri Kanekar
<meetgaurikanekar(at)gmail(dot)com> wrote:
> Andrew,
>
> Can you explain me in detail why u said vacuum full is making the things
> worst.
1. VACUUM FULL takes exclusive lock on the table. That makes table
unavailable for read/writes.
2. VACUUM FULL moves live tuples around. When a tuple is moved, the
old index entry is deleted and a new index entry is inserted. This
causes index bloats which are hard to recover.
> We do vacuum full, as vacuum verbose analyse dont regain space for us.
>
As I mentioned in the other reply, you are not gaining much by
regaining space. The subsequent UPDATEs/INSERTs will quickly extend
the relation and you loose all the work done by VACUUM FULL. Plain
VACUUM will update FSM to track the free space scattered across the
relation which is later reused by updates/inserts.
Thanks,
Pavan
--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com
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