Jim Nasby wrote: > On Jul 25, 2006, at 3:31 PM, Tom Lane wrote: > >Hannu Krosing <[EMAIL PROTECTED]> writes:
> >>What would be the use-case for hash indexes ? And what should be > >>done to make them faster than btree ? > > > >If we knew, we'd do it ;-) But no one's put enough effort into it > >to find out. > > Do they use the same hash algorithm as hash joins/aggregation? If so, > wouldn't hash indexes be faster for those operations than regular > indexes? The main problem doesn't seem to be in the hash algorithm (which I understand to mean the hashing function), but in the protocol for concurrent access of index pages, and the distribution of keys in pages of a single hash key. This is described in a README file or a code comment somewhere in the hash AM code. Someone needs to do some profiling to find out what the bottleneck really is, and ideally find a way to fix it. -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc. ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
