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.
/ Oskari