Re: GIN improvements part 1: additional information

Attached version of patch is debugged. I would like to note that number of bugs was low and it wasn't very hard to debug. I've rerun tests on it. You can see that numbers are improved as the result of your refactoring.

         event         |     period

-----------------------+-----------------

 index_build           | 00:01:45.416822

 index_build_recovery  | 00:00:06

 index_update          | 00:05:17.263606

 index_update_recovery | 00:01:22

 search_new            | 00:24:07.706482

 search_updated        | 00:26:25.364494

(6 rows)

     label      | blocks_mark

----------------+-------------

 search_new     |   847587636

 search_updated |   881210486

(2 rows)

     label     |   size

---------------+-----------

 new           | 419299328

 after_updates | 715915264

(2 rows)

Beside simple bugs, there was a subtle bug in incremental item indexes update. I've added some more comments including ASCII picture about how item indexes are shifted.

Now, I'm trying to implement support of old page format. Then we can decide which approach to use.