Julius Tuskenis <jul...@nsoft.lt> writes:
>  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.

No, it does not.  That function property *allows* the optimizer to
invoke the function fewer times than would happen in an un-optimized
query.  It does not *require* it to do so.  There is no such cache
mechanism in Postgres, and it's unlikely that there ever will be,
because it probably would be a net performance loss on average.

                        regards, tom lane

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