Matthew Wakeling <matthew@flymine.org> wrote:
> I have implemented the very same algorithm in both a Postgres GiST
> extension and as a standalone Java program. In general, the
> standalone Java program performs about 100 times faster than
> Postgres when running a large index-based nested loop join.
>
> I profiled Postgres a few weeks back, and found a large amount of
> time being spent in fmgr_oldstyle.
I've seen the code in Java outperform the same code in optimized C,
because the "just in time" compiler can generate native code optimized
for the actual code paths being taken rather than a compile-time guess
at that, but a factor of 100? Something else has to be going on here
beyond an interface layer. Is this all in RAM with the Java code,
versus having disk access in PostgreSQL?
-Kevin