Re: Why does query planner choose slower BitmapAnd ?

From: Seamus Abshere <seamus(at)abshere(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, pgsql-general(at)postgresql(dot)org
Subject: Re: Why does query planner choose slower BitmapAnd ?
Date: 2016-02-22 17:53:38
Message-ID: 1456163618.1013318.528482610.2E35A103@webmail.messagingengine.com
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On Mon, Feb 22, 2016, at 02:49 PM, Tom Lane wrote:
> Seamus Abshere <seamus(at)abshere(dot)net> writes:
> > Inspired, I changed cpu_index_tuple_cost to 0.1 (default: 0.005). It "fixed" my problem by preventing the BitmapAnd.
> > Is this dangerous?
>
> Use a gentle tap, man, don't swing the hammer with quite so much abandon.
> I'd have tried doubling the setting to start with. Raising it 20X might
> cause other queries to change behavior undesirably.

Doubling it was enough :)

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