Check parallel safety in generate_useful_gather_paths
Commit ebb7ae839d ensured we ignore pathkeys with volatile expressions
when considering adding a sort below a Gather Merge. Turns out we need
to care about parallel safety of the pathkeys too, otherwise we might
try sorting e.g. on results of a correlated subquery (as demonstrated
by a report from Luis Roberto).
Initial investigation by Tom Lane, patch by James Coleman. Backpatch
to 13, where the code was instroduced (as part of Incremental Sort).
Reported-by: Luis Roberto
Author: James Coleman
Reviewed-by: Tomas Vondra
Backpatch-through: 13
Discussion: https://postgr.es/m/622580997.37108180.1604080457319.JavaMail.zimbra%40siscobra.com.br
Discussion: https://postgr.es/m/CAAaqYe8cK3g5CfLC4w7bs=hC0mSksZC=H5M8LSchj5e5OxpTAg@mail.gmail.com
Branch
------
REL_13_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/be9c3cd186ba86b9bc3df7ecc64b81ce4726810d
Modified Files
--------------
src/backend/optimizer/path/allpaths.c | 13 +++++++--
src/backend/optimizer/path/equivclass.c | 9 +++++-
src/include/optimizer/paths.h | 5 +++-
src/test/regress/expected/incremental_sort.out | 40 ++++++++++++++++++++++++++
src/test/regress/sql/incremental_sort.sql | 11 +++++++
5 files changed, 73 insertions(+), 5 deletions(-)
