On Wed, Jun 22, 2016 at 5:16 AM, Ashutosh Bapat <ashutosh.ba...@enterprisedb.com> wrote: >> However, if we support deparsing subqueries, the remote query in the above >> example could be rewritten into something like this: >> >> SELECT ss.c2 FROM t1 LEFT JOIN (SELECT t2.a, ROW(a, b) FROM t2) ss(c1, c2) >> ON (t1.a = ss.c1); >> >> So we would no longer need "CASE WHEN r2.* IS NOT NULL THEN ROW(r2.a, >> r2.b) END" in the target list in the remote query. > > Right. Although, it means that the query processor at the other end has to > do extra work for pulling up the subqueries.
I would be inclined to pick the method that generates cleaner SQL. I doubt that difference in optimization speed matters here - it's presumably very small, especially when compared to the cost of the network round-trip. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
