Hello, Merlin
Thank you for your quick response.
2011.03.10 23:14, Merlin Moncure rašė:
This is a huge problem with non trivial functions in the select list.
Pushing the result into and a subquery does NOT guarantee that the
inner result is materialized first.
From the postgresql documentation about STABLE functions: "
This category allows the optimizer to optimize multiple calls of the function to a single call." I thought that this means that optimizer executes the function only for now parameter sets and stores results in some "cache" and use it if the parameters are already known. I realize this is very naive approach and most probably everything is much more complicated. I would appreciate if someone would explain the mechanism (or provide with some useful link).
Try a CTE.
with foo as
( select yadda;
)
select func(foo.a), foo.* from foo;
I'm sorry, but I'm totally new to CTE. Would you please show me how should I use the stable function and where the parameters should be put to improve the behavior of the optimizer for my problem?
Thank you in advance
--
Julius Tuskenis
Programavimo skyriaus vadovas
UAB nSoft
mob. +37068233050
