returning json object with subset of keys

Hi

I'm using the json functionalities of postgresql 9.3.
I have a query calling json_populate_recordset like this:
  json_populate_recordset(null::product, event->'products')
but it returns an error:
ERROR:  cannot call json_populate_recordset on a nested object

There is indeed one key in event->'products' giving access to an array of objects.

Is there a way to specify which keys to keep from the object? I haven't found ti in the docs.

Here is pseudo code of what I'd like to do:
  json_populate_recordset(null::product, event->'products' WITH ONLY KEYS {'f1','f2'})

Thx 


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