I quote Andrew Dunstan on the pgsql-hackers list:
At some stage there will possibly be some json-processing (as opposed to json-producing) functions, but not in 9.2.
Doesn't prevent him from providing an example implementation in PLV8 that should solve your problem.
Offers an arsenal of new functions and operators to add "json-processing".
The answer to the original question in Postgres 9.3:
SELECT *
FROM json_array_elements(
'[{"name": "Toby", "occupation": "Software Engineer"},
{"name": "Zaphod", "occupation": "Galactic President"} ]'
) AS elem
WHERE elem->>'name' = 'Toby';
Advanced example:
For bigger tables you may want to add an expression index to increase performance:
Adds jsonb (b for "binary", values are stored as native Postgres types) and yet more functionality for both types. In addition to expression indexes mentioned above, jsonb also supports GIN, btree and hash indexes, GIN being the most potent of these.
json and jsonb data types and functions.The manual goes as far as suggesting:
In general, most applications should prefer to store JSON data as
jsonb, unless there are quite specialized needs, such as legacy assumptions about ordering of object keys.
Bold emphasis mine.
Performance benefits from general improvements to GIN indexes.
Complete jsonb functions and operators. Add more functions to manipulate jsonb in place and for display.