Greg Stark <st...@mit.edu> writes: > On Thu, Sep 22, 2016 at 3:23 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> But to kick the hash AM as such to the curb is to say >> "sorry, there will never be O(1) index lookups in Postgres".
> Well there's plenty of halfway solutions for that. We could move hash > indexes to contrib or even have them in core as experimental_hash or > unlogged_hash until the day they achieve their potential. > We definitely shouldn't discourage people from working on hash indexes > but we probably shouldn't have released ten years worth of a feature > marked "please don't use this" that's guaranteed to corrupt your > database and cause weird problems if you use it a any of a number of > supported situations (including non-replicated system recovery that > has been a bedrock feature of Postgres for over a decade). Obviously that has not been a good situation, but we lack a time machine to retroactively make it better, so I don't see much point in fretting over what should have been done in the past. > Arguably adding a hashed btree opclass and relegating the existing > code to an experimental state would actually encourage development > since a) Users would actually be likely to use the hashed btree > opclass so any work on a real hash opclass would have a real userbase > ready and waiting for delivery, b) delivering a real hash opclass > wouldn't involve convincing users to unlearn a million instructions > warning not to use this feature and c) The fear of breaking existing > users use cases and databases would be less and pg_upgrade would be an > ignorable problem at least until the day comes for the big cutover of > the default to the new opclass. I'm not following your point here. There is no hash-over-btree AM and nobody (including Andres) has volunteered to create one. Meanwhile, we have a patch in hand to WAL-enable the hash AM. Why would we do anything other than apply that patch and stop saying hash is deprecated? regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers