Re: Red-black tree for GIN

On Thu, Dec 31, 2009 at 4:19 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> My other question is as related to performance.  Can you provide a
> test case that shows the performance improvement with this patch?

So, we still don't have a test case for this patch. During the
November CommitFest, Greg Smith griped a bit about the lack of a
reproducible performance benchmark for the XLogInsert patch:

http://archives.postgresql.org/pgsql-hackers/2009-12/msg00816.php

...and I would say the same logic applies to this patch, maybe even
moreso. Tom has already applied a partial workaround for this
problem, and I'm feeling like it won't be trivial to figure out what
to measure to see the remaining issue and measure how much this new
implementation helps.

The coding pattern that this patch uses also merits some discussion.
Basically, rbtree.c is a generic implementation of red-black trees -
from a textbook - which ginbulk.c then uses for GIN. One possible
advantage of this implementation is that it might make it possible for
us to use the rbtree.c logic in other places, if we have other data
structures that need similar treatment. But I'm not sure if that's
the way we want to go. The other alternative is to drop the
generalized implementation and incorporate the logic directly into
ginbulk.c. I really don't know which is better, but I'd like to hear
some other opinions...

...Robert