It's a key-value store that allows querying, which is what I think you are lamenting in your comment. Here's a bit more about how to query and index with hstore: http://lwn.net/Articles/406385/. It's pretty simple and doesn't have anywhere near the number of querying possibilities that MongoDB has, but it can be used for on-the-fly column names (similar to JSON). You can only query on the root node's children, unlike the open-ended possibilities in NoSQL.
It's a key-value store that allows querying, which is what I think you are lamenting in your comment. Here's a bit more about how to query and index with hstore: http://lwn.net/Articles/406385/. It's pretty simple and doesn't have anywhere near the number of querying possibilities that MongoDB has, but it can be used for on-the-fly column names (similar to JSON). You can only query on the root node's children, unlike the open-ended possibilities in NoSQL.