Thread: pgsql: Fix an old corner-case error in match_unsorted_outer(): don't

pgsql: Fix an old corner-case error in match_unsorted_outer(): don't

From
tgl@postgresql.org (Tom Lane)
Date:
Log Message:
-----------
Fix an old corner-case error in match_unsorted_outer(): don't consider
the cheapest-total inner path as a new candidate while truncating the
sort key list, if it already matched the full sort key list.  This is
too much of a corner case to be worth back-patching, since it's unusual
for the cheapest total path to be sorted, and anyway no real harm is
done (except in JOIN_SEMI/ANTI cases where cost_mergejoin is a bit
broken at the moment).  But it wasn't behaving as intended, so fix it.
Noted while examining a test case from Kevin Grittner.  This error doesn't
explain his issue, but it does explain why "set enable_seqscan = off"
seemed to reproduce it for me.

Modified Files:
--------------
    pgsql/src/backend/optimizer/path:
        joinpath.c (r1.120 -> r1.121)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/joinpath.c?r1=1.120&r2=1.121)