Hi! Thank you for your work on this subject.
I have reviewed your patch and I think it is better to add an Assert for
JOIN_RIGHT_SEMI to the ExecMergeJoin and ExecNestLoop functions to
prevent the use of RIGHT_SEMI for these types of connections (NestedLoop
and MergeJoin).
Mostly I'm suggesting this because of the set_join_pathlist_hook
function, which is in the add_paths_to_joinrel function, which allows
you to create a custom node. What do you think?
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Regards,
Alena Rybakina
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company