From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Jeevan Chalke <jeevan.chalke@enterprisedb.com>
Cc: pgsql-hackers@lists.postgresql.org, David Rowley <david.rowley@2ndquadrant.com>
Subject: Re: Soon-to-be-broken regression test case
Date: Thu, 11 Oct 2018 13:19:11 -0400
Message-ID: <8265.1539278351@sss.pgh.pa.us> (raw)
In-Reply-To: <20181011165251.k7ggwmvmlfjv33gr@alvherre.pgsql>
References: <20181011165251.k7ggwmvmlfjv33gr@alvherre.pgsql>
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> On 2018-Oct-11, Tom Lane wrote:
>> Hm, I'm not seeing any regression test result changes there. However,
>> if you're just executing queries and not EXPLAIN'ing them, it's possible
>> something unwanted is happening under the hood.
> Hmm, no, the explains are there. Here's one example -- maybe your new
> planner smarts do not change these plans for some reason
Oh, I see --- these are just "scalar-result sub-SELECTs", not
sub-select-in-FROM, so they never get into the join tree to begin with.
WHERE EXISTS is an exception because we attempt to translate it to a
JOIN_SEMI join, exposing an opportunity for subquery pullup.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, alvherre@2ndquadrant.com, robertmhaas@gmail.com, jeevan.chalke@enterprisedb.com, david.rowley@2ndquadrant.com
Subject: Re: Soon-to-be-broken regression test case
In-Reply-To: <8265.1539278351@sss.pgh.pa.us>
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