Comment by panzi
9 months ago
Not sure why those are json_agg() instead of array_agg() in that example. Why would you use a JSON array instead of a native properly typed array? Yes, if you have some complex objects for some reason you can use JSON objects. But those where all just arrays of IDs. Also why was it json_agg() and not jsonb_agg()? Is there any reason on why to use JSON over JSONB in PostgreSQL?
If you, for whatever obscure reason, need to preserve whitespace and key ordering, that is you want something that is effectively just a text column, then you should use JSON over JSONB.
I can't think of any case at all, no matter how contrived, where you'd want to use the non-B versions of the JSON aggregate functions though.
The non-B JSON can take up less space on disk and less write time complexity.
I wonder if its just used in a query like that if the generated data structure is only in memory anyway and then serialized to JSON to send to the client. I.e. JSON VS JSONB would not make any difference?