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Re: Index bloat problem?

From: John A Meinel <john(at)arbash-meinel(dot)com>
To: Bill Chandler <billybobc1210(at)yahoo(dot)com>,pgsql-performance(at)postgresql(dot)org
Subject: Re: Index bloat problem?
Date: 2005-04-21 23:54:08
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Lists: pgsql-performance
Bill Chandler wrote:

>Thanks.  Yes, I understand that not having a large
>enough max_fsm_pages is a problem and I think that it
>is most likely the case for the client.  What I wasn't
>sure of was if the index bloat we're seeing is the
>result of the "bleeding" you're talking about or
>something else.
>If I deleted 75% of the rows but had a max_fsm_pages
>setting that still exceeded the pages required (as
>indicated in VACUUM output), would that solve my
>indexing problem or would I still need to REINDEX
>after such a purge?
I don't believe VACUUM re-packs indexes. It just removes empty index
pages. So if you have 1000 index pages all with 1 entry in them, vacuum
cannot reclaim any pages. REINDEX re-packs the pages to 90% full.

fsm just needs to hold enough pages that all requests have free space
that can be used before your next vacuum. It is just a map letting
postgres know where space is available for a new fill.


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