Excluding nulls from row_to_json() result in PostgreSQL

Question

I want to convert the rows of a record set to JSON, but not include any null entries that are just going to end up being undefined in JavaScript anyway. For example, suppose I have the table testdata with entries

id | prop1 (integer) | prop2 (text)
-------------------------------------
 1 |               42 | 'Answer'
 2 |             NULL | 'No prop one'
 3 |                0 | NULL

and then execute

SELECT row_to_json(testdata) FROM testdata

What I get is:

{"id":"1","prop1":"42","prop2":"Answer"}
{"id":"2","prop1":null,"prop2":"No prop one"}
{"id":"3","prop1":"0","prop2":null}

But instead, what I want is:

{"id":"1","prop1":"42","prop2":"Answer"}
{"id":"2","prop2":"No prop one"}
{"id":"3","prop1":"0"}

Is this possible? According to the JSON functions documentation for PostgreSQL 9.3, there's only one extra option or parameter for row_to_json, but setting pretty_bool=true doesn't remove the nulls, so it seems as if the answer may be no. But this also seems as if it's a very obvious and useful function, so I'm hoping that somebody else has found something I've missed.

My end goal is to retrieve the records in JavaScript with a GET call to a PHP page. Am I better off building the JSON in PHP from a more standard recordset, instead of using PostgreSQL's JSON routines?

Answer 1

Postgres 9.5 introduces json_strip_nulls function, that seems to do exactly what you want.

Answer 2

Looks like future versions of the function may have an 'ignore nulls' option - https://commitfest.postgresql.org/action/patch_view?id=1496