Re: 9.3 Pre-proposal: Range Merge Join

On Thu, 2013-01-17 at 21:03 +0100, Stefan Keller wrote:
> Hi Jeff

> I'm perhaps really late in this discussion but I just was made aware
> of that via the tweet from Josh Berkus about "PostgreSQL 9.3: Current
> Feature Status"
>
> What is the reason to digg into spatial-joins when there is PostGIS
> being a bullet-proof and fast implementation?
>

Hi Stefan,

You are certainly not too late.

PostGIS uses the existing postgres infrastructure to do spatial joins.
That mean it either does a cartesian product and filters the results, or
it uses a nested loop with an inner index scan.

That isn't too bad, but it could be better. I am trying to introduce a
new way to do spatial joins which will perform better in more
circumstances. For instance, we can't use an inner index if the input
tables are actually subqueries, because we can't index a subquery.

Regards,
Jeff Davis