Re: GIN Index for low cardinality

From: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
To: Olleg Samoylov <splarv(at)ya(dot)ru>
Cc: srkrishna1(at)aol(dot)com, pgsql-general(at)lists(dot)postgresql(dot)org
Subject: Re: GIN Index for low cardinality
Date: 2018-10-26 22:55:31
Message-ID: CAMkU=1xEFJnhZJxtNHTOBknwrHFFfqGvGSEd=Dp2uW8nOhQenA@mail.gmail.com
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On Fri, Oct 26, 2018 at 12:27 PM Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:

Here is a real-world example from one of my databases where each value is
> about 17 characters long, and is present about 20 times:
>
> gin: 411 MB
> btree: 2167 MB
> hash: 2159 MB
>

For what it is worth, that was 9.6 with freshly rebuilt indexes.

On 11.0 with freshly rebuilt indices, the hash index does get a bit smaller:

gin: 411 MB
btree: 2167 MB
hash: 1864 MB

Cheers,

Jeff
>
>

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