"How does Postgres even index an hstore?" It allows normal btree indexing of, for example, the values for some given key by using functional and/or partial ind

"How does Postgres even index an hstore?" It allows normal btree indexing of, for example, the values for some given key by using functional and/or partial indexes. It also allows indexing of "contains", "contains key", "contains all of these keys" and "contains some of these keys" by using GiST and GIN indexes.