On Thu, Apr 6, 2017 at 4:37 PM, Tomas Vondra <tomas.von...@2ndquadrant.com> wrote: > Which brings me to the slightly suspicious bit. On 9.5, there's no > difference between GROUP and GROUP+LIKE cases - the estimates are exactly > the same in both cases. This is true too, but only without the foreign key > between "partsupp" and "part", i.e. the two non-grouped relations in the > join. And what's more, the difference (1737 vs. 16) is pretty much exactly > 100x, which is the estimate for the LIKE condition.
I don't follow this. How does the foreign key between partsupp and part change the selectivity of LIKE? > So it kinda seems 9.5 does not apply this condition for semi-joins, while >>=9.6 does that. If 9.5 and prior are ignoring some of the quals, that's bad, but I don't think I understand from your analysis why 7fa93eec4e0c9c3e801e3c51aa4bae3a38aaa218 regressed anything. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers