Using the famous WAG tech, in your first query the optimizer has to evaluate monitored for each record to determine its value.
Robert Treat On Thu, 2002-11-21 at 13:39, Daniele Orlandi wrote: > > Are those two syntaxes eqivalent ? > > select * from users where monitored; > select * from users where monitored=true; > > If the answer is yes, the optimimer probably doesn't agree with you :) > > Tested on RC1: > > template1=# create table a (a boolean, b text); > CREATE TABLE > > > .... inserted ~18000 rows with just one true (just to make an index scan > meaningful).... > > template1=# vacuum analyze a; > VACUUM > template1=# explain select * from a where a; > QUERY PLAN > ---------------------------------------------------- > Seq Scan on a (cost=0.00..802.64 rows=1 width=11) > Filter: a > (2 rows) > > template1=# explain select * from a where a=true; > QUERY PLAN > -------------------------------------------------------------- > Index Scan using a_a on a (cost=0.00..2.01 rows=1 width=11) > Index Cond: (a = true) > (2 rows) > > Bye! > > -- > Daniele Orlandi > Planet Srl > > > ---------------------------(end of broadcast)--------------------------- > TIP 5: Have you checked our extensive FAQ? > > http://www.postgresql.org/users-lounge/docs/faq.html ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
