Disallow UNION/INTERSECT/EXCEPT over no columns. Since 9.4, we've allowed the syntax "select union select" and variants of that. However, the planner wasn't expecting a no-column set operation and ended up treating the set operation as if it were UNION ALL.
Pre-v10, there seem to be some executor issues that would need to be fixed to support such cases, and it doesn't really seem worth expending much effort on. Just disallow it, instead. Per report from Victor Yegorov. Discussion: https://postgr.es/m/cagnebojgjrrsogjwngm7jsjzpvaf8xxcvpbvrgdhbvehz-b...@mail.gmail.com Branch ------ REL9_6_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/bd29bc417e7130312b47ba0da244c020a0193694 Modified Files -------------- src/backend/optimizer/prep/prepunion.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
