Jie Zhang wrote: > > IIRC they quoted the cardinality of 10000 as something that is still > > faster than btree for several usecases. > > > > And also for AND-s of several indexes, where indexes are BIG, your btree > > indexes may be almost as big as tables but the resulting set of pages is > > small. > > Yeah, Hannu points it out very well -- the bitmap index works very well when > columns have low cardinalities and AND operations will produce small number > of results.
What operations on columns of low cardinality produce a small number of results? That seems contradictory. > Also, the bitmap index is very small in low cardinality cases, where the > btree tends to take up at least 10 times more space. Also, are adding/changing rows is more expensive with bitmaps than btrees? -- Bruce Momjian [EMAIL PROTECTED] EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
