Re: json (b) and null fields

Andrew, all,

* Andrew Dunstan (andrew@dunslane.net) wrote:
> I should have been paying a bit more attention to the recent work on
> adding an ignore_nulls option to row_to_json(). Here are some
> belated thought. I apologize to Pavel and Stephen for not having
> commented earlier.

No problem at all and thanks for continuing to think about it!  We
certainly still have quite a bit of time til 9.5 to get this right.

> I think this is really a bandaid, and it will fail to catch lots of
> cases. Several examples:

As discussed on IRC- I agree.  I tend to think of JSON objects as
relatively simple hstore-like structures and so hadn't considered the
complex structure case (as I'm guessing Pavel hadn't either).

> I think a much more comprehensive solution would be preferable. What
> I have in mind is something like
>
>     json_strip_null_fields(json) -> json
>
> and a similar function for jsonb.

Right, this makes sense to me.

> These would operate recursively. There is a downside, in that they
> would be required to reprocess the json/jsonb. But adding an option
> like this to all the json generator functions would be seriously
> ugly, especially since they are mostly aggregate functions or
> variadic functions. At least in the jsonb case the cost of
> reprocessing is likely to be fairly low.

Yeah, I don't see adding this option to all json generator functions as
making a lot of sense but rather just to the select few things which it
really makes sense for and then having a function which can be used by
users to do the same for results from other operations.
Thanks!
    Stephen