Re: Index Skip Scan

From: Dmitry Dolgov <9erthalion6(at)gmail(dot)com>
To: Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, Alexander Kuzmenkov <a(dot)kuzmenkov(at)postgrespro(dot)ru>
Cc: Peter Geoghegan <pg(at)bowt(dot)ie>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Bhushan Uparkar <bhushan(dot)uparkar(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, James Coleman <jtc331(at)gmail(dot)com>
Subject: Re: Index Skip Scan
Date: 2019-01-26 17:45:54
Message-ID: CA+q6zcVFc3+Wm_EfsEif5oy9HKxA+wm9Z2iPSzecSCBKANg5Mw@mail.gmail.com
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> On Thu, Dec 20, 2018 at 2:46 PM Dmitry Dolgov <9erthalion6(at)gmail(dot)com> wrote:
>
> I've performed some testing, and on my environment with a dataset of 10^7
> records:
>
> * everything below 7.5 * 10^5 unique records out of 10^7 was faster with skip
> scan.
>
> * above 7.5 * 10^5 unique records skip scan was slower, e.g. for 10^6 unique
> records it was about 20% slower than the regular index scan.
>
> For me these numbers sound good, since even in quite extreme case of
> approximately 10 records per group the performance of index skip scan is close
> to the same for the regular index only scan.

Rebased version after rd_amroutine was renamed.

Attachment Content-Type Size
0001-Index-skip-scan-v6.patch application/octet-stream 44.8 KB

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