PostgreSQL: Documentation: 8.4: hstore. From the series "Things your database can do that you might not know": Key-Value-Stores within a PostgreSQL data field. Or also poor-mans-object-notation. Or simply practical when you want to store loosely structured data but don't want to constantly adjust the schema - the schema is then the primary data for the order of the model, the dependencies, cardinalities, etc. - and the hstore field then stores the additional manifestations that, for example, result dynamically from business requirements. Sometimes the better alternative to a denormalized property table. And it's been there since the 8.x versions (though it is a loadable module).