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.
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