Re: [SQL] querying with index on jsonb slower than standard column. Why? - Mailing list pgsql-performance

From Tom Lane
Subject Re: [SQL] querying with index on jsonb slower than standard column. Why?
Date
Msg-id 4746.1418073776@sss.pgh.pa.us
Whole thread Raw
In response to Re: [SQL] querying with index on jsonb slower than standard column. Why?  (Adrian Klaver <adrian.klaver@aklaver.com>)
Responses Re: [SQL] querying with index on jsonb slower than standard column. Why?  (Adrian Klaver <adrian.klaver@aklaver.com>)
List pgsql-performance
Adrian Klaver <adrian.klaver@aklaver.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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