Re: [GENERAL] How do you control IMMUTABLE PG PROC results?

2010-11-04 Thread hubert depesz lubaczewski 
On Thu, Nov 04, 2010 at 08:24:14PM -0400, Carlo Stonebanks wrote:
> We have procs that would benefit from returning IMMUTABLE results.
> The procs are dependent on external tables that rarely change, but
> when they DO change, it would be great if we could expire the cache
> that the procs read from so that the procs are forced to re-evaluate
> the results.
> 
> Is this possible?
> 
> How do I know how many possible results are cached?

in addition to what Leif responded, please note that immutable functions
*do not* cache results.

depesz

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Re: [GENERAL] How do you control IMMUTABLE PG PROC results?

2010-11-04 Thread Leif Biberg Kristensen 
On Friday 5. November 2010 01.24.14 Carlo Stonebanks wrote:
> We have procs that would benefit from returning IMMUTABLE results. The procs 
> are dependent on external tables that rarely change, but when they DO 
> change, it would be great if we could expire the cache that the procs read 
> from so that the procs are forced to re-evaluate the results.

A function declared as IMMUTABLE can't, by definition, do database lookups. 
Then it has to be declared as STABLE.



«An IMMUTABLE function cannot modify the database and is guaranteed to return 
the same results given the same arguments forever.»

regards,
Leif B. Kristensen

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