Re: [COMMITTERS] pgsql: Compress GIN posting lists, for smaller index size.

On 01/22/2014 06:28 PM, Heikki Linnakangas wrote:
> Compress GIN posting lists, for smaller index size.
>
> GIN posting lists are now encoded using varbyte-encoding, which allows them
> to fit in much smaller space than the straight ItemPointer array format used
> before. The new encoding is used for both the lists stored in-line in entry
> tree items, and in posting tree leaf pages.
>
> To maintain backwards-compatibility and keep pg_upgrade working, the code
> can still read old-style pages and tuples. Posting tree leaf pages in the
> new format are flagged with GIN_COMPRESSED flag, to distinguish old and new
> format pages. Likewise, entry tree tuples in the new format have a
> GIN_ITUP_COMPRESSED flag set in a bit that was previously unused.
>
> This patch bumps GIN_CURRENT_VERSION from 1 to 2. New indexes created with
> version 9.4 will therefore have version number 2 in the metapage, while old
> pg_upgraded indexes will have version 1. The code treats them the same, but
> it might be come handy in the future, if we want to drop support for the
> uncompressed format.
>
> Alexander Korotkov and me. Reviewed by Tomas Vondra and Amit Langote.

it seems that this commit made spoonbill an unhappy animal:

http://www.pgbuildfarm.org/cgi-bin/show_log.pl?nm=spoonbill&dt=2014-01-23%2000%3A00%3A04

Stefan