Hi, The item on hash indexes reminded me of an old comment from years ago that I put in the code of the first custom PG datatype I ever built at $work:
COMMENT ON OPERATOR CLASS puid_ops USING btree IS 'As puids are only identifiers, there is no obvious reason to define ordering operators or support btree indexing. But for some curious reason PostgreSQL 8.4 does not allow a hash index to support UNIQUE constraints (this may be because, per the manual, hash index "operations are not presently WAL-logged" so it could be risky to base constraints on them). Therefore, the whole set of ordering operators must be implemented to provide an operator class for the btree index method.'; Was my guess about the reason right? Does this PG10 announcement also mean it will be possible to use UNIQUE constraints with some pure-identifier, no-natural-ordering type that supports only hashing? -Chap -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
