From: | Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Tim Dudgeon <tdudgeon(dot)ml(at)gmail(dot)com>, pgsql-sql(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: querying with index on jsonb slower than standard column. Why? |
Date: | 2014-12-08 21:34:38 |
Message-ID: | 5486196E.4080602@aklaver.com |
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Lists: | pgsql-performance pgsql-sql |
On 12/08/2014 01:22 PM, Tom Lane wrote:
> Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> writes:
>> I redid the test on my 32-bit machine, setting work_mem=16MB, and I got
>> comparable results to what I saw on the 64-bit machine. So, what I am
>> still am puzzled by is why work_mem seems to make the two paths
>> equivalent in time?:
>
> If work_mem is large enough that we never have to go through
> tbm_lossify(), then the recheck condition will never be executed,
> so its speed doesn't matter.
Aah, peeking into tidbitmap.c is enlightening. Thanks.
>
> (So the near-term workaround for Tim is to raise work_mem when
> working with tables of this size.)
>
> regards, tom lane
>
>
--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com
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