On 06/05/2015 02:32 PM, Alvaro Herrera wrote:
'some jsonb value' - '{foo,bar}' is already ambiguous - the RH operand could be a single text datum or a text array.Hmm, but that's not in 9.4, so we can still tweak it if necessary.Consider this jsonb datum. Nobody in their right mind would have a key that looks like a path, I hear you say; yet I'm sure this is going to happen. alvherre=# select jsonb '{"a":"1", "b":"2", "c": {"a": "2"}, "{c,a}": "uh"}' ; jsonb ------------------------------------------------------ {"a": "1", "b": "2", "c": {"a": "2"}, "{c,a}": "uh"} (1 fila) This seems pretty surprising to me: -- here, the -(jsonb,text) operator is silently chosen, even though the -- right operand looks like an array. And we do the wrong thing. alvherre=# select jsonb '{"a":"1", "b":"2", "c": {"a": "2"}}' - '{c,a}'; ?column? --------------------------------------- {"a": "1", "b": "2", "c": {"a": "2"}} (1 fila) -- here, the -(jsonb,text[]) operator is chosen alvherre=# select jsonb '{"a":"1", "b":"2", "c": {"a": "2"}}' - _text '{c,a}'; ?column? ------------------------------- {"a": "1", "b": "2", "c": {}} (1 fila) But this seems worse to me, because we silently do nothing: alvherre=# select jsonb '{"a":"1", "b":"2", "c": {"a": "2"}}' - '{c,a}'; ?column? --------------------------------------- {"a": "1", "b": "2", "c": {"a": "2"}} (1 fila) I think the first operator can be qualified as dangerous. If you delete that one, then it's fine because you can't do that query anymore because of the conflict with -(jsonb, int). alvherre=# select jsonb '{"a":"1", "b":"2", "c": {"a": "2"}}' - '{c,a}'; ERROR: operator is not unique: jsonb - unknown LÍNEA 1: ...elect jsonb '{"a":"1", "b":"2", "c": {"a": "2"}}' - '{c,a}'... ^ SUGERENCIA: Could not choose a best candidate operator. You might need to add explicit type casts.
Yeah, Good point. Actually, if my memory serves me correctly (always a dubious bet), the avoidance of that kind of ambiguity is why we introduced the #> and #>> operators in the first place, after going round and round for a while on what the API would look like. I should have remembered that when this came around. Mea culpa.
So probably the least invasive change would be to rename the text[] variant operator to something like "#-" and rename the corresponding function to jsonb_delete_path.
We could also decide not to keep an operator at all, on the ground that we think we'll implement a type that encapsulates json pointer in 9.6, and just keep the renamed function.
cheers andrew -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
