Fix 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.
Turns out it's trivial to fix in v10 and later; we just need to be careful
about not generating a Sort node with no sort keys. However, since a weird
corner case like this is never going to be exercised by developers, we'd
better have thorough regression tests if we want to consider it supported.
Per report from Victor Yegorov.
Discussion: https://postgr.es/m/CAGnEbojGJrRSOgJwNGM7JSJZpVAf8xXcVPbVrGdhbVEHZ-BUMw@mail.gmail.com
Branch
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master
Details
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https://git.postgresql.org/pg/commitdiff/c4c2885cbb1803f772e58f6db4c8951d8cd672cd
Modified Files
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src/backend/optimizer/plan/createplan.c | 1 -
src/backend/optimizer/prep/prepunion.c | 26 +++-----
src/test/regress/expected/union.out | 115 ++++++++++++++++++++++++++++++++
src/test/regress/sql/union.sql | 43 ++++++++++++
4 files changed, 168 insertions(+), 17 deletions(-)
