Re: Planning large IN lists

"Atul Deopujari" <atul(dot)deopujari(at)enterprisedb(dot)com> writes:
> Hi,
> Tom Lane wrote:
>> That's the least of the problems. We really ought to convert such cases
>> into an IN (VALUES(...)) type of query, since often repeated indexscans
>> aren't the best implementation.
>>
> I thought of giving this a shot and while I was working on it, it
> occurred to me that we need to decide on a threshold value of the IN
> list size above which such transformation should take place.

I see no good reason to suppose that there is/should be a constant
threshold --- most likely it depends on size of table, availability of
indexes, etc. Having the planner try it both ways and compare costs
would be best.

regards, tom lane