How to convert postgres json to integer

Question

I can use to_json(1) to cast int to json, but how can I convert json to int? This may be too slow:

to_json(1)::text::int 

Also, is json wrapped from a binary block (bson) or a simple wrapper of text?

Answer 1

What works for me (using posgtgresql 5.6) is

SELECT (tablename.jsoncolumnname->>'jsonfiledname')::int FROM tablename; 

like

SELECT (users.data->>'failed_login_attempts_count')::int FROM users; 

Assuming users table has a json column named data which is something like:

{"failed_login_attempts_count":"2","comment":"VIP"} 

Answer 2

to_json(1)::text::int maybe too slow

But then, it's the only way.

The second part of your question is unclear.