Using as a starting point the old bitmap patch in: http://archives.postgresql.org/message-id/20081101000154.go27...@fune
I re-applied and re-worked the patch to see what kind of improvements over btrees bitmaps actually provided. Using a 20M rows table of 10/100/1000 random values, I've found that: 1) bulk index creation time is roughly 6 times better 2) index size is 6-15 times smaller (depending on column cardinality) 3) there's almost no difference in query times (but I have to make more tests) 4) I can't say anything about the insertion performance, but I guess bitmap will perform way worse than btree Are these improvements (index creation time, index size) worth enough to keep on working on this? I mean: given that bitmaps don't give any benefits in query times, but only benefits related to disk size and bulk index creation times, and will have horrible performance for insertions/deletions: would this job be worthed? In case it is: I will try to clean up the patch and post it... As a side note: I guess that most of the bitmap indexes performance improvements in the SELECT area are already implemented in postgres in the bitmapand/or and bitmap scan stuff? I couldn't find any docs that say that bitmap indexes are faster for selects, unless of course they are ANDed/ORed together (which is something postgres already does for regular btree indexes) -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
