Re: Ad Hoc Indexes

Justin <justin@emproshunts.com> writes:
> The idea of ad hoc indexes is speed up loop scans  To prove my idea i 
> created a sql file in PGAdmin that creates the indexes on the fly then 
> runs the query then drops the indexs.

>  without the indexes it takes 18 to 19 seconds to run the query.

> To create the index and do the query takes 400 milliseconds.

The example you show doesn't convince me of much of anything, because
the estimated rowcounts are so far off.  I think you're basically
dealing with an estimation failure and it's pure luck that the extra
index fixes it.
        regards, tom lane