PostgreSQL 9.4 will be reintroducing Hstore as the column type of choice for document-style data. This supersedes PostgreSQL’s JSON support which was introduced in version 9.0. Being a string-based representation, JSON is significantly slower than the binary structure of HStore. And with the addition of Boolean and integer support, the new Hstore is semantically equivalent to JSON. In practical terms this allows two-way conversions between the formats using just a casting operator.