From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> |
Cc: | Tim Dudgeon <tdudgeon(dot)ml(at)gmail(dot)com>, pgsql-sql(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: [SQL] querying with index on jsonb slower than standard column. Why? |
Date: | 2014-12-08 21:22:56 |
Message-ID: | 4746.1418073776@sss.pgh.pa.us |
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Lists: | pgsql-performance pgsql-sql |
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.
(So the near-term workaround for Tim is to raise work_mem when
working with tables of this size.)
regards, tom lane
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