Re: [HACKERS] [PATCHES] GIN improvements

[Teodor Sigaev]

New version. Changes:
 - synced with current CVS
 - added all your changes
 - autovacuum will run if fast update mode is turned on and
   trigger of fresh tuple is fired
 - gincostestimate now tries to calculate cost of scan of pending pages.
   gincostestimate set disable_cost if it believe that tidbitmap will
   become lossy. So, tidbitmap has new method - estimation of
   maximum number of tuples with guaranteed non-lossy mode.

START_CRIT_SECTION();
...
l = PageAddItem(...);
if (l == InvalidOffsetNumber)
    elog(ERROR, "failed to add item to index page in \"%s\"",
         RelationGetRelationName(index));

It's no use using ERROR, because it will turn into PANIC, which is

I did that similar to other GIN/GiST places. BTW, BTree  directly emits PANIC if
PageAddItem fails

4. Heikki mentioned:
http://archives.postgresql.org/pgsql-hackers/2008-11/msg01832.php



That issue still remains, correct? Is there a resolution to that?

"To make things worse, a query will fail if all the matching fast-inserted tuples don't fit in the non-lossy tid bitmap."

Now gincostestimate can forbid index scan by disable_cost (see Changes). Of course, it doesn't prevent failure in case of large update (for example), but it prevents in most cases. BTW, because of sequential scan of pending list cost of scan grows up fast and index scan becomes non-optimal.

5. I attached a newer version merged with HEAD.

Thank you

6. You defined:

#define GinPageHasFullRow(page) ( GinPageGetOpaque(page)->flags &
GIN_LIST_FULLROW )

Fixed

7.  I don't understand this chunk of code:

How can (!ItemPointerEquals(&pos->item, &item)) ever happen?

And how can (scanGetCandidate(scan, pos) == false) ever happen? Should
that be an Assert() instead?

If those can happen during normal operation, then we need a better error
message there.

It should be assert, but assert enabled and disabled code will be different :(.


--
Teodor Sigaev                                   E-mail: teo...@sigaev.ru
                                                   WWW: http://www.sigaev.ru/

In both cases, scanGetCandidate() should be called, but in assert enabled code we need to check return value and pos->item.

fast_insert_gin-0.20.gz
Description: Unix tar archive

-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers