Re: GIN improvements part 1: additional information

On Sat, Jun 29, 2013 at 12:56 PM, Heikki Linnakangas <
hlinnakangas(at)vmware(dot)com> wrote:

> There's a few open questions:
>
> 1. How are we going to handle pg_upgrade? It would be nice to be able to
> read the old page format, or convert on-the-fly. OTOH, if it gets too
> complicated, might not be worth it. The indexes are much smaller with the
> patch, so anyone using GIN probably wants to rebuild them anyway, sooner or
> later. Still, I'd like to give it a shot.
>
> 2. The patch introduces a small fixed 32-entry index into the packed
> items. Is that an optimal number?
>
> 3. I'd like to see some performance testing of insertions, deletions, and
> vacuum. I suspect that maintaining the 32-entry index might be fairly
> expensive, as it's rewritten on every update to a leaf page.

It appears that maintaining 32-entry index is really expensive because it
required re-decoding whole page. This issue is fixed in attached version of
patch by introducing incremental updating of that index. Benchmarks will be
posted later today.

------
With best regards,
Alexander Korotkov.