Re: Unexplainable execution time difference between two test functions...one using IF (SELECT COUNT(*) FROM...) and the other using IF EXISTS (SELECT 1 FROM...)

From: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
To: Hackety Man <hacketyman(at)gmail(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Pgsql Performance <pgsql-performance(at)lists(dot)postgresql(dot)org>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>
Subject: Re: Unexplainable execution time difference between two test functions...one using IF (SELECT COUNT(*) FROM...) and the other using IF EXISTS (SELECT 1 FROM...)
Date: 2018-04-17 20:30:47
Message-ID: bd907ab8-74ea-383f-b547-0928154a11ac@2ndquadrant.com
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On 04/17/2018 04:05 PM, Hackety Man wrote:
> Hi Pavel,
>
> Thanks for sharing that information.  I was not aware that the parallel
> query functionality was not yet fully implemented.
>

Nothing is ever "fully implemented". There are always gaps and possible
improvements ;-)

That being said, parallelism opens an entirely new dimension of possible
plans and planning issues.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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