Hi Andres and Greg, > I think they're almost unused and don't offer enough advantage over btree
I largely agree with this. In my experience, B-tree accounts for 95%+ of indexes, and all other access methods combined make up only a small fraction. But I do see quite a few hash index users. > we should have just ripped them out. I have mixed feelings on this. On one hand, hash is probably the least used "general-purpose" index since its use case overlaps directly with B-tree, whereas GiST, SP-GiST, and BRIN exist for specialized data types or access patterns that B-tree can't handle. On the other hand, in practice I still see hash indexes used at least as often as GiST, BRIN, or SP-GiST. I suspect part of the low adoption is historical baggage from being unlogged prior to old version, which gave hash indexes a bad reputation in the community, it also miss some features for general OLTP workloads I feel there is plenty of room for improvement there. > The advantage hash does have, i.e. large key handling, would have better been > addressed by adding support to transparently btree indexing a hash of the key + recheck. That's an interesting point. But I think users can do that today with expression index right? Thanks, Shihao
