From 215824f9188a2b19f870e6a707c5a81e1ac3f1fc Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sun, 26 Jan 2020 14:31:08 -0500 Subject: In postgres_fdw, don't try to ship MULTIEXPR updates to remote server. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In a statement like "UPDATE remote_tab SET (x,y) = (SELECT ...)", we'd conclude that the statement could be directly executed remotely, because the sub-SELECT is in a resjunk tlist item that's not examined for shippability. Currently that ends up crashing if the sub-SELECT contains any remote Vars. Prevent the crash by deeming MULTIEXEC Params to be unshippable. This is a bit of a brute-force solution, since if the sub-SELECT *doesn't* contain any remote Vars, the current execution technology would work; but that's not a terribly common use-case for this syntax, I think. In any case, we generally don't try to ship sub-SELECTs, so it won't surprise anybody that this doesn't end up as a remote direct update. I'd be inclined to see if that general limitation can be fixed before worrying about this case further. Per report from Lukáš Sobotka. Back-patch to 9.6. 9.5 had MULTIEXPR, but we didn't try to perform remote direct updates then, so the case didn't arise anyway. Discussion: https://postgr.es/m/CAJif3k+iA_ekBB5Zw2hDBaE1wtiQa4LH4_JUXrrMGwTrH0J01Q@mail.gmail.com --- contrib/postgres_fdw/sql/postgres_fdw.sql | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'contrib/postgres_fdw/sql/postgres_fdw.sql') diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index acd7275c729..83971665e35 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -1191,6 +1191,26 @@ DELETE FROM ft2 RETURNING 100; DELETE FROM ft2 WHERE ft2.c1 > 1200; +-- Test UPDATE with a MULTIEXPR sub-select +-- (maybe someday this'll be remotely executable, but not today) +EXPLAIN (verbose, costs off) +UPDATE ft2 AS target SET (c2, c7) = ( + SELECT c2 * 10, c7 + FROM ft2 AS src + WHERE target.c1 = src.c1 +) WHERE c1 > 1100; +UPDATE ft2 AS target SET (c2, c7) = ( + SELECT c2 * 10, c7 + FROM ft2 AS src + WHERE target.c1 = src.c1 +) WHERE c1 > 1100; + +UPDATE ft2 AS target SET (c2) = ( + SELECT c2 / 10 + FROM ft2 AS src + WHERE target.c1 = src.c1 +) WHERE c1 > 1100; + -- Test UPDATE/DELETE with WHERE or JOIN/ON conditions containing -- user-defined operators/functions ALTER SERVER loopback OPTIONS (DROP extensions); -- cgit v1.2.3