Re: Use of index for 50% column restriction

From: Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Use of index for 50% column restriction
Date: 2016-06-14 20:24:12
Message-ID: 8d7c9f3a-93d3-a1e0-164b-d2f32a5a5f20@BlueTreble.com
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On 6/8/16 4:36 PM, Bruce Momjian wrote:
> Just a follow-up, but even with a randomized correlation order, it seems
> 25% restrictivity generates a Bitmap Index Scan:

AFAIK we do the bitmap heap scan in heap order, thereby eliminating the
effect of correlation?
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
855-TREBLE2 (855-873-2532) mobile: 512-569-9461

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