Don't assume a subquery's output is unique if there's a SRF in its tlist.
While the x output of "select x from t group by x" can be presumed unique,
this does not hold for "select x, generate_series(1,10) from t group by x",
because we may expand the set-returning function after the grouping step.
(Perhaps that should be re-thought; but considering all the other oddities
involved with SRFs in targetlists, it seems unlikely we'll change it.)
Put a check in query_is_distinct_for() so it's not fooled by such cases.
Back-patch to all supported branches.
David Rowley
Branch
------
REL9_4_STABLE
Details
-------
http://git.postgresql.org/pg/commitdiff/ac45aa1dde2dd690682bf74f7535ba6d1a87bff8
Modified Files
--------------
src/backend/optimizer/util/pathnode.c | 11 ++++++++++
src/test/regress/expected/subselect.out | 35 +++++++++++++++++++++++++++++++
src/test/regress/sql/subselect.sql | 9 ++++++++
3 files changed, 55 insertions(+)