You don't need an index to select rows based on the contents of a json document in 9.3. You may want or need them depending on your queries. (I use them sparing

You don't need an index to select rows based on the contents of a json document in 9.3. You may want or need them depending on your queries. (I use them sparingly, the most common pattern for me is that an indexed non-json column filters a query down to a smaller set of rows, and then a further index on the attributes referenced in the query isn't necessary.) And if you do want to create an index now on a JSON attribute in 9.3, a function isn't necessary.