On 31.03.2025 06:04, David Rowley wrote:
On Mon, 31 Mar 2025 at 15:33, Alena Rybakina<a.rybak...@postgrespro.ru> wrote:
I believe it's worth asserting that both inner_unique and single_mode are not
true at the same time — just as a safety check.
add_paths_to_joinrel() just chooses not to populate inner_unique for
SEMI and ANTI joins because, as of today's master, it's pretty
pointless to determine that because the executor will short-circuit
and skip to the next outer tuple for those join types anyway. I don't
follow why having both these flags set would cause trouble. It seems
perfectly legitimate that add_paths_to_joinrel() could choose to set
the inner_unique flag for these join types, and if it did, the Assert
you're proposing would fail for no good reason.
I tend to agree with you that someone might set this flag to true for
these join types in the future.
However, is it necessary to check that extra->inner_unique must be false
for SEMI/ANTI joins here, or am I missing something? It looks a little
confusing at this point.
if(!extra->inner_unique&& (jointype== JOIN_SEMI|| jointype== JOIN_ANTI))
single_mode= true;
--
Regards,
Alena Rybakina
Postgres Professional
