On Sun, Jan 7, 2024 at 3:03 PM vignesh C <vignes...@gmail.com> wrote:
> One of the tests in CFBot has failed at [1] with: > - Relations: (public.ft1 t1) SEMI JOIN (public.ft2 t2) > - Remote SQL: SELECT r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, r1.c6, > r1.c7, r1.c8 FROM "S 1"."T 1" r1 WHERE ((r1."C 1" < 20)) AND EXISTS > (SELECT NULL FROM "S 1"."T 1" r3 WHERE ((r3."C 1" > 10)) AND > ((date(r3.c5) = '1970-01-17'::date)) AND ((r3.c3 = r1.c3))) ORDER BY > r1."C 1" ASC NULLS LAST > -(4 rows) > + Sort Key: t1.c1 > + -> Foreign Scan > + Output: t1.c1, t1.c2, t1.c3, t1.c4, t1.c5, t1.c6, t1.c7, t1.c8 > + Relations: (public.ft1 t1) SEMI JOIN (public.ft2 t2) > + Remote SQL: SELECT r1."C 1", r1.c2, r1.c3, r1.c4, r1.c5, > r1.c6, r1.c7, r1.c8 FROM "S 1"."T 1" r1 WHERE ((r1."C 1" < 20)) AND > EXISTS (SELECT NULL FROM "S 1"."T 1" r3 WHERE ((r3."C 1" > 10)) AND > ((date(r3.c5) = '1970-01-17'::date)) AND ((r3.c3 = r1.c3))) > +(7 rows) Thanks. I looked into it and have figured out why the plan differs. With this patch the SEMI JOIN that is pushed down to the remote server is now implemented using JOIN_RIGHT_SEMI, whereas previously it was implemented using JOIN_SEMI. Consequently, this leads to changes in the costs of the paths: path with the sort pushed down to remote server, and path with the sort added atop the foreign join. And at last the latter one wins by a slim margin. I think we can simply update the expected file to fix this plan diff, as attached. Thanks Richard
v4-0001-Support-Right-Semi-Join-plan-shapes.patch
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