On 06/06/16 18:30, David G. Johnston wrote: > To clarify, the present behavior is basically a combination of both of > Robert's results. > > If the SRFs return the same number of rows the first (zippered) result > is returned without an NULL padding. > > If the SRFs return a different number of rows the LCM behavior kicks in > and you get Robert's second result.
No. > SELECT generate_series(1, 4), generate_series(1, 4) ORDER BY 1, 2; > is the same as > SELECT * FROM ROWS FROM ( generate_series(1, 4), generate_series(1, 4) ); > > BUT > > SELECT generate_series(1, 3), generate_series(1, 4) ORDER BY 1, 2; > is the same as > SELECT * FROM ROWS FROM generate_series(1, 3) a, LATERAL ROWS FROM > generate_series(1, 4) b; What would you do with: SELECT generate_series(1, 3), generate_series(1, 6); ? > Tom's 2.5 proposal basically says we make the former equivalence succeed > and have the later one fail. > > The rewrite would be unaware of the cardinality of the SRF and so it > cannot conditionally rewrite the query. One of the two must be chosen > and the incompatible behavior turned into an error. -- Vik Fearing +33 6 46 75 15 36 http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers