Re: Index-only scan returns incorrect results when using a composite GIST index with a gist_trgm_ops column.

Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> writes:
> At Wed, 24 Jan 2018 00:13:51 +0300, Sergei Kornilov <sk(at)zsrv(dot)org> wrote in <348951516742031(at)web54j(dot)yandex(dot)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_idx"
>> 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