| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Abi Noda <a(at)abinoda(dot)com> |
| Cc: | Justin Pryzby <pryzby(at)telsasoft(dot)com>, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, pgsql-performance(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Why isn't an index scan being used? |
| Date: | 2019-02-20 14:58:22 |
| Message-ID: | CAMkU=1zrAsD4apC3rED+O7BuFL_82tL6LYNGTMfqAyWQ1D0LBw@mail.gmail.com |
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| Lists: | pgsql-performance |
On Tue, Feb 19, 2019 at 11:59 PM Abi Noda <a(at)abinoda(dot)com> wrote:
> Thanks Justin.
>
> The 4ms different in the examples isn't an accurate benchmark. I'm seeing
> about a ~20% difference over a larger sample size. And this is on a fork of
> the production database.
>
Please show the execution plans from that larger sample, if that is the one
that is most relevant.
You can "set enable_bitmapscan = off" to get rid of the bitmap scan in
order to see the estimated cost and actual performance of the next-best
plan (which will probably the regular index scan).
Cheers,
Jeff
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