Thread: pgsql: Consider parallel awareness when removing single-child Appends
Consider parallel awareness when removing single-child Appends 8edd0e794 added some code to remove Append and MergeAppend nodes when they contained a single child node. As it turned out, this was unsafe to do when the Append/MergeAppend was parallel_aware and the child node was not. Removing the Append/MergeAppend, in this case, could lead to the child plan being called multiple times by parallel workers when it was unsafe to do so. Here we fix this by just not removing the Append/MergeAppend when the parallel_aware flag of the parent and child node don't match. Reported-by: Yura Sokolov Bug: #17335 Discussion: https://postgr.es/m/b59605fecb20ba9ea94e70ab60098c237c870628.camel%40postgrespro.ru Backpatch-through: 12, where 8edd0e794 was first introduced Branch ------ REL_14_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/357ff66153b4791d32c45724d8a0d3c91d89c937 Modified Files -------------- src/backend/optimizer/plan/setrefs.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)