2011/1/10 Mladen Gogala <mladen.gogala@xxxxxxxxxxx>: > Well, I really hoped that Bruce, Robert or Greg would take on this one, but > since there are no more qualified takers, I'll take a shot at this one. For > the "NOT IN (result of a correlated sub-query)", the sub-query needs to be > executed for every row matching the conditions on the driving table, while > the !EXISTS is just a complement of join. It's all in the basic set theory > which serves as a model for the relational databases. As Scott says, the real problem is the NULL handling. The semantics are otherwise similar. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
