I'm simply referring to literature (like the intro Ramakrishnan & Gehrke). I just know that Oracle an Mysql actually do have them too and use it without those current implementation specific restrictions in Postgres. IMHO by design Hash Index (e.g. linear hashing) work best when: 1. only equal (=) tests are used (on whole values) 2. columns (key values) have very-high cardinality And ideally but not necessarily when index values do not change and number of rows are known ahead of time (avoiding O(N) worst case - but there are approaches to chaining with dynamic resizing). I just collected this to encourage ourselves that enhancing hash indexes could be worthwhile. Stefan 2011/9/18 Kevin Grittner <Kevin.Grittner@xxxxxxxxxxxx>: > Stefan Keller wrote: > >> It's hard for me to imagine that btree is superior for all the >> issues mentioned before. > > It would be great if you could show a benchmark technique which shows > otherwise. > > -Kevin > -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
