Re: Why performance improvement on converting subselect to a function ?

Dear Tom,

the problem was repeatble in the sense repeated
execution of queries made no difference on
performance.

What lead to degradation was the bumping off of
effective_cache_size parameter from 1000 to 64K

Can any one point me the recent guide done by
Sridhar and Josh i want to see what i mis(read|understood)
from there ;-) [ it was on GeneralBits' Home Page ]

Anyway the performance gain was from 32 secs to less
than a sec what i restored cache size from 64K to 1000.

I will post again with more details but at the moment
i got to load my data_bank :)

Regds
Mallah.

On Wednesday 30 Jul 2003 3:02 am, Tom Lane wrote:
> Rajesh Kumar Mallah <mallah(at)trade-india(dot)com> writes:
> > Tom Lane wrote:
> >> Odd. Apparently the planner is picking a better plan in the function
> >> context than in the subselect context --- which is strange since it
> >> ought to have less information.
> >
> > [ verbose plan snipped ]
>
> Well, that sure seems to be the same plan. Curious that the runtime
> wasn't about the same. Perhaps the slow execution of the first query
> was a caching effect? If you alternate trying the query both ways,
> does the speed difference persist?
>
> regards, tom lane