On Sun, Dec 20, 2015 at 11:14:46PM -0300, Alvaro Herrera wrote: > Jim Nasby wrote: > > On 11/23/15 5:06 PM, Peter Geoghegan wrote: > > >I realize that the second scan performed by lazy_vacuum_heap() only > > >visits those pages known to contain dead tuples. However, the > > >experience of seeing problems with the random sampling of ANALYZE > > >makes me think that that might not be very helpful. There is no good > > >reason to think that there won't be a uniform distribution of dead > > >tuples across the heap, and so only visiting pages known to contain > > >dead tuples might be surprisingly little help even when there are > > >relatively few VACUUM-able tuples in the table. > > > > Even worse is if you can't fit all the dead TIDs in memory and have to do > > multiple passes for no reason... > > Since BRIN indexes cannot be primary keys nor unique keys, it's hard to > be convinced that the use case of a table with only BRIN indexes is > terribly interesting.
If you've got high-frequency logs, timestamptz might not operate at fine enough a grain to form a primary key, but it's just the kind of thing BRIN is great at narrowing down. Cheers, David. -- David Fetter <da...@fetter.org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david.fet...@gmail.com Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers