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Comment by azdle | Hacker News Reader

Why would this cause problems? Order is irrelevant in JSON. "An object is an unordered set of name/value pairs."[0] From a there is absolutely no difference between {"name": "Patrick", "age": 24} and {"age": 24, "name": "Patrick"}.

[0] http://json.org/

EDIT: Well, now four of us have replied at the same time saying the same thing, I'd say this topic is now well covered.

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Sometimes it matters whether serialization to a string is a deterministic function. If the JSON is the same, you want the output to be the same. A JSON parser won't care, but it's useful to do a string comparison without parsing (for example when diffing output).

But that's not really a correct thing to expect is it? If an object is an unordered set of name/value pairs then multiple serialized versions of the object may indeed be the same object data.

It's not something you can assume, but sorting the keys is sometimes a desirable feature in a JSON serializer. (Just like pretty-printing is.)

AFAIK the default serializer does not guarantee the order to be stable, but I haven't participated in the development of this feature that closely. So maybe I'm wrong.

Anyway, it should be possible to write a simple serializer on your own - a trivial PL/V8 function should suffice, I guess. And then you can define a CAST using that function (but generally adding casts is a bit dangerous, as it may have unexpected consequences).

Of course, it is still an interesting question of whether it would be practically stable in Postgres or not.

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