Re: [HACKERS] Big IN() clauses etc : feature proposal

On Wed, May 10, 2006 at 04:38:31PM +0200, PFC wrote:
> You need to do some processing to know how many rows the function
> would return.
> Often, this processing will be repeated in the function itself.
> Sometimes it's very simple (ie. the function will RETURN NEXT each
> element in an array, you know the array length...)
> Sometimes, for functions returning few rows, it might be faster to
> compute the entire result set in the cost estimator.

I think the best would probably be to assign a constant. An SRF will
generally return between one of 1-10, 10-100, 100-1000, etc. You don't
need exact number, you just need to get within an order of magnitude
and a constant will work fine for that.

How many functions sometimes return one and sometimes a million rows?

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.