Can we write retrieving only 10 records from 4000 records plz tell me asap On Mar 23, 8:28 pm, [EMAIL PROTECTED] (Tom Lane) wrote: > Giorgio Valoti <[EMAIL PROTECTED]> writes: > > Are there any way to pass some hints to the planner? For example, > > could the IMMUTABLE/STABLE/VOLATILE modifiers be of some help? > > Those don't really do anything for set-returning functions at the > moment. > > As of 8.3 there is a ROWS attribute for SRFs that can help with one > of the worst problems, namely that the planner has no idea how many > rows a SRF might return. It's simplistic (just an integer constant > estimate) but better than no control at all. > > As of CVS HEAD (8.4 to be) there's a capability in the planner to > "inline" SRFs that are single SELECTs in SQL language, which should > pretty much eliminate the performance differential against a comparable > view. Unfortunately 8.4 release is at least a year away, but just > so you know. (I suppose if you were desperate enough to run a privately > modified copy, that patch should drop into 8.3 easily enough.) IIRC > the restrictions for this to happen are > * single SELECT > * function declared to return set > * function NOT declared strict or volatile > * function NOT declared SECURITY DEFINER or given any > local parameter settings > The latter restrictions are needed so that inlining doesn't change > the semantics. > > regards, tom lane > > - > Sent via pgsql-performance mailing list ([EMAIL PROTECTED]) > To make changes to your > subscription:http://www.postgresql.org/mailpref/pgsql-performance
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