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From: Tomas Vondra <tv@fuzzy.cz>
To: pgsql-hackers@postgresql.org
Subject: Re: GIN improvements part 1: additional information
Date: Sat, 12 Oct 2013 18:15:57 +0200
Message-ID: <525975BD.3080403@fuzzy.cz> (raw)
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On 12.10.2013 12:11, Alexander Korotkov wrote:
> On Sat, Oct 12, 2013 at 1:55 AM, Tomas Vondra <tv@fuzzy.cz
> <mailto:tv@fuzzy.cz>> wrote:
> 
>     Yup, this version fixed the issues. I haven't been able to do any
>     benchmarks yet, all I have is some basic stats
> 
>                    |   HEAD   |  patched
>     ======================================
>     load duration  |  1084 s  |   1086 s
>     subject index  |   96 MB  |     96 MB
>     body index     | 2349 MB  |   2051 MB
> 
>     So there's virtually no difference in speed (which is expected, AFAIK)
>     and the large index on full message bodies is significantly smaller.
> 
> 
> Yes, it should be no significant difference in speed. But difference in
> index sizes seems to be too small. Could you share database dump somewhere?

Turns out that if I do VACUUM FULL after loading the data (a sequence of
INSERT commands), the index sizes drop significantly.

                   |   HEAD   |  patched
    ======================================
    subject index  |   42 MB  |    15 MB
    body index     |  624 MB  |   328 MB

So there's a significant improvement, as expected. I'm wondering if the
bloat is expected too? Is that the consequence of incremental index
updates vs. rebuilding the whole index at once during VACUUM FULL?

Tomas


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