postgres_fdw could support row comparison pushdown

From: Alexander Pyhalov <a(dot)pyhalov(at)postgrespro(dot)ru>
To: Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: postgres_fdw could support row comparison pushdown
Date: 2023-08-07 14:02:39
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postgres_fdw currently doesn't handle RowCompareExpr, which doesn't
allow keyset pagination queries to be efficiently executed over sharded
Attached patch adds handling of RowCompareExpr in deparse.c, so that we
could push down conditions like
WHERE (created, id) > ('2023-01-01 00:00:00'::timestamp, 12345) to the
foreign server.

I'm not sure about conditions when it's possible for RowCompareExpr to
have opnos with different names or namespaces, but comment in
ruleutils.c suggests that this is possible, so I've added check for this
in foreign_expr_walker().
Best regards,
Alexander Pyhalov,
Postgres Professional

Attachment Content-Type Size
0001-postgres_fdw-support-RowCompareExpr-pushdown.patch text/x-diff 8.3 KB

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