Re: GIN improvements part 1: additional information

On Thu, Oct 3, 2013 at 10:48 PM, Robert Haas <robertmhaas@gmail.com> wrote:

On Thu, Oct 3, 2013 at 2:43 PM, Heikki Linnakangas
<hlinnakangas@vmware.com> wrote:
> It seems we've all but decided that we'll require reindexing GIN indexes in
> 9.4.

I thought the consensus in Ottawa was strongly against that.  I'm not
aware that anyone has subsequently changed their position on the
topic.  Bruce is right to point out that we've done such things before
and can therefore do it again, but just because we have the technical
means to do it doesn't make it good policy.

That having been said, if we do decide to break it...

> Let's take the opportunity to change some other annoyances with the
> current GIN on-disk format:

...then fixing as much as possible in one go-round is clearly a good plan.

Let's see what options we have at all. I see following:

1) Drop support old GIN on-disk format. But users will have to reindex after pg_upgrade.

2) Insert kluges into GIN to support both old and new formats. So, kluges are kluges :) I don't see elegant way to do it for now, because formats are very different.

3) Upgrade GIN on-disk format in pg_upgrade. However, it would be rewriting almost whole index. Is it much better than just reindex?

4) Fork GIN2, leave GIN as is. It would lead to much of duplicated code.

Any other options?