From: Tom Lane <tgl@sss.pgh.pa.us>
To: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
cc: sk@zsrv.org, michael.paquier@gmail.com, x4mmm@yandex-team.ru,
        david@nlpgo.com, pgsql-bugs@lists.postgresql.org,
        pgsql-hackers@postgresql.org
Subject: Re: Index-only scan returns incorrect results when using a composite
 GIST index with a gist_trgm_ops column.
In-reply-to: <20180124.161153.214591193.horiguchi.kyotaro@lab.ntt.co.jp>
References: <20180118082505.GA84508@paquier.xyz>
 <20180118.211449.240575561.horiguchi.kyotaro@lab.ntt.co.jp>
 <348951516742031@web54j.yandex.ru>
 <20180124.161153.214591193.horiguchi.kyotaro@lab.ntt.co.jp>
Comments: In-reply-to Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
	message dated "Wed, 24 Jan 2018 16:11:53 +0900"
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Date: Thu, 01 Mar 2018 15:39:18 -0500
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Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> writes:
> At Wed, 24 Jan 2018 00:13:51 +0300, Sergei Kornilov <sk@zsrv.org> wrote =
in <348951516742031@web54j.yandex.ru>
>> Should we also make backport to older versions? I test on REL_10_STABLE=
 - patch builds and works ok, but "make check" fails on new testcase with =
error:
> CREATE INDEX ON t USING gist (a test_inet_ops, a inet_ops);
> + ERROR:  missing support function 4 for attribute 1 of index "t_a_a1_id=
x"
>> and with different explain results.

> Thank you for checking that. d3a4f89 allowed that and
> inet_gist_decompress is removed at the same time. Unfortunately I
> didn't find a type on master that has both decompress and fetch
> methods so I prefer to split the regression patch among target
> versions.

I pushed this fix with minor adjustments.  I did not like the proposed
regression test at all: it was overcomplicated and the need for different
versions for different back branches wasn't fun either.  After some poking
around I found that the bug could be exhibited using just btree_gist's
gist_inet_ops, since the core inet_ops class indexes the same datatype and
it does have a fetch function.  So I added a test case in btree_gist.

			regards, tom lane