Re: function optimization ???

On 24 Jan 2001 at 12:14 (-0500), Tom Lane wrote:
| Brent Verner <brent@rcfile.org> writes:
| > calling it as:
| >   SELECT p.*, p.book_info.title FROM pricing p WHERE vista_ans='POD';
| > background and observation:
| >   the pricing table is fairly large, but only a small number meet
| >   "WHERE vista_ans='POD'". I can select all where vista_ans='POD'
| >   very quickly (.2 sec), but adding in the get_book(pricing) call
| >   slows this down to about 20sec. I can, with an external sql query,
| >   select all of the desired records in about 1 sec, so it appears
| >   to me that the function is being called regardless of whether
| >   or not the WHERE clause is being satisfied.
| 
| This conclusion is absolutely false: the SELECT target list is NOT
| evaluated except at rows where the WHERE condition is satisfied.
| 
| I suspect the real problem is that the select inside the function
| is not being done as efficiently as you'd like.

yes, this is indeed the case. Sorry for the noise, my 'with an external
query' case was a broken product of sleep-dep :\.

thanks. brent