Re: IN list processing performance (yet again)

Mario Weilguni wrote:

My application relies heavily on IN lists.  The lists are primarily
constant integers, so queries look like:

SELECT val FROM table WHERE id IN (43, 49, 1001, 100002, ...)

Performance is critical, and the size of these lists depends a lot on
how the larger 3-tier applicaiton is used,
but it wouldn't be out of the question to retrieve 3000-10000 items.

PostgreSQL 7.3.2 seems to have a lot of trouble with large lists.   

you should rewrite your query if the query is created from an applition:

SELECT val  FROM tableWHERE id between 43 and 100002      AND id IN (43, 49, 1001, 100002, ...)

where 43 is the min and 100002 the max of all values.

I had this case with postgresql 7.2 and the planner made much smarter
choices in my case.

Regards,   Mario Weilguni 

Very interesting!  I tried it out, but it didn't appreciably change the thresholds in my results for going by for IN list
sizes 100 - 1000.  It's also likely to be of use only if the range for the between is fairly restricted,
which isn't necessarily characteristic of my data.

Dave