On 2016-09-21 19:49:15 +0300, Oskari Saarenmaa wrote: > 21.09.2016, 15:29, Robert Haas kirjoitti: > > For PostgreSQL, I expect the benefits of improving hash indexes to be > > (1) slightly better raw performance for equality comparisons and (2) > > better concurrency. > > There's a third benefit: with large columns a hash index is a lot smaller on > disk than a btree index. This is the biggest reason I've seen people want > to use hash indexes instead of btrees. hashtext() btrees are a workaround, > but they require all queries to be adjusted which is a pain.
Sure. But that can be addressed, with a lot less effort than fixing and maintaining the hash indexes, by adding the ability to do that transparently using btree indexes + a recheck internally. How that compares efficiency-wise is unclear as of now. But I do think it's something we should measure before committing the new code. Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
