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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Julien Rouhaud <rjuju123@gmail.com>
Cc: Thomas Munro <thomas.munro@gmail.com>
Cc: Marc Cousin <cousinmarc@gmail.com>
Cc: Alexander Korotkov <a.korotkov@postgrespro.ru>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Nikita Glukhov <n.gluhov@postgrespro.ru>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Avoid full GIN index scan when possible
Date: Thu, 01 Aug 2019 10:37:06 -0400
Message-ID: <12611.1564670226@sss.pgh.pa.us> (raw)
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	<CAOBaU_ZCg4955_HGcQZdn44wtTQRpiHkLgkVsxqQ5cfymDL-XQ@mail.gmail.com>
	<20190628161051.szk2kxmue6yjdmra@development>
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	<4547.1561748599@sss.pgh.pa.us>
	<20190628195401.frwhcga76rrytbc4@development>
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	<eca8612b-e289-e2fc-c5df-84be46f75ec1@gmail.com>
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Julien Rouhaud <rjuju123@gmail.com> writes:
> Attached v4 that should address all comments.

Eyeing this a bit further ... doesn't scanPendingInsert also need
to honor so->forcedRecheck?  Something along the lines of

-			tbm_add_tuples(tbm, &pos.item, 1, recheck);
+			tbm_add_tuples(tbm, &pos.item, 1, recheck | so->forcedRecheck);

at line 1837?  (Obviously, there's more than one way you could
write that.)

I'm also not exactly satisfied with the new comments --- they aren't
conveying much, and the XXX in one of them is confusing; does that
mean you're unsure that the comment is correct?

The added test case seems a bit unsatisfying as well, in that it
fails to retrieve any rows.  It's not very clear what it's
trying to test.

			regards, tom lane





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