Re: [GENERAL] Optimizing "exists"

2007-09-18 Thread Tom Lane
Steve Crawford <[EMAIL PROTECTED]> writes: > If the sub-select returns a large result set, will there be any benefit > to adding "limit 1" to the sub-select or does the query planner > automatically deduce that "limit 1" is the correct interpretation? It does, although poking at it I notice a bit

[GENERAL] Optimizing "exists"

2007-09-18 Thread Steve Crawford
Does the planner automatically add "limit 1" to "exists" sub-selects? In other words, take an update like: update foo set itexists = exists (select 1 from bar where bar.something = foo.something); If the sub-select returns a large result set, will there be any benefit to adding "limit 1" to th