Re: query looping?

On Mon, Jan 4, 2010 at 2:41 PM, Brian Cox <brian(dot)cox(at)ca(dot)com> wrote:
> The query shown below [select count(distinct...] seems to be looping
> (99-101% CPU as shown by top for 11+ hours). This using postgres 8.3.5 on a
> dual quad core machine (Intel(R) Xeon(R) CPU X5460 @ 3.16GHz) with 32G RAM.
> Can I provide any other info to help investigate this issue? Or any thoughts
> on how to prevent/avoid it?

You posted an EXPLAIN ANALYZE showing almost the same query taking 17
seconds, but a crucial difference is that the EXPLAIN ANALYZE shows
the query with the parameters actually in the query, whereas the query
that's actually running for a long time uses bound parameters.
PostgreSQL won't take the particular values into account in planning
that version, which can sometimes lead to a markedly inferior plan.

What do you get if you do this?

PREPARE foo AS <the query, with the $x entries still in there>
EXPLAIN EXECUTE foo(<the values>);

...Robert