On Thu, Feb 10, 2011 at 6:21 PM, Nicolas Barbier <nicolas.barb...@gmail.com> wrote: > 2011/2/10 mac_man2...@yahoo.it <mac_man2...@yahoo.it>: > >> Which operations invoke the sorting algorithms implemented in the sorting >> module (tuplesort.c) ? >> Of course, one of those operations invoking sorting is the ORDER BY clause >> and the DISTINCT too. >> >> Moreover, the Merge Join should be implemented invoking sorting. >> >> Is there any other operation invoking sorting? > > AFAIK, all set operators except for UNION ALL. (I am probably missing > a whole boatload of other things.)
Merge joins don't necessarily involve a sort - you could do a merge over a pair of index scans, for example. Set operations can be implemented using hashing or sorting, too. -- 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