David Johnston <polobo@xxxxxxxxx> writes: > The two comparable queries are: > A) WITH vf ( SELECT volatile_function(x) FROM generate_series(1,10) ) > SELECT * FROM vf LIMIT 1 > B) SELECT volatile_function(x) FROM generate_series(1,10) gs (x) LIMIT 1 > In (A) the relation "vf" - which is a 10-row table with the result of > volatile_function as the only column - is limited to a single record and > that whole row is output as-is (because of the "*") > In (B) the relation "gs" - which is 10 rows having the result of > generate_series as the only column - is limited to a single row and then the > select-list project occurs against that single row (the volatile_function) Just for the record, your interpretation of (B) is wrong. LIMIT acts after select-list evaluation --- try a set-returning function in the select list to see that this is true. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
