On Mon, Mar 14, 2011 at 7:40 PM, Greg Stark <gsst...@mit.edu> wrote: > On Mon, Mar 14, 2011 at 8:33 PM, Robert Haas <robertmh...@gmail.com> wrote: >> I'm not sure about that either, although I'm not sure of the reverse >> either. But before I invest any time in it, do you have any other >> good ideas for addressing the "it stinks to scan the entire index >> every time we vacuum" problem? Or for generally making vacuum >> cheaper? > > You could imagine an index am that instead of scanning the index just > accumulated all the dead tuples in a hash table and checked it before > following any index link. Whenever the hash table gets too big it > could do a sequential scan and prune any pointers to those tuples and > start a new hash table.
Hmm. For something like a btree, you could also remove each TID from the hash table when you kill the corresponding index tuple. > That would work well if there are frequent vacuums finding a few > tuples per vacuum. It might even allow us to absorb dead tuples from > "retail" vacuums so we could get rid of line pointers earlier. But it > would involve more WAL-logged operations and incur an extra overhead > on each index lookup. Yeah, that seems deeply unfortunate. It's hard to imagine us wanting to go there. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
