Re: json (b) and null fields

On 09/27/2014 06:27 PM, Tom Lane wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>> On 09/27/2014 08:00 AM, Stephen Frost wrote:
>>> 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.
>> I guess I'm questioning the wisdom of keeping it for row_to_json given
>> that it doesn't operate recursively anyway (and making it do so would be
>> difficult and ugly).
> IMO, adding it to row_to_json was really ugly to start with, independently
> of whether it's difficult or not. That function had one too many optional
> arguments already, and in its current form it's nothing but a loaded gun
> pointed at users' feet. (Quick, which bool argument is which?)
>
>> If we're going to keep this, I think we also need to provide it
>> (non-recursive) for json_agg via an optional second argument. This
>> should be a fairly simple change: just steer the result via
>> composite_to_json if it's a record, rather than to datum_to_json.
> Unfortunately, any such thing will fall foul of an established project
> policy. I quote the opr_sanity regression test that will complain:
>
> -- Check that there are not aggregates with the same name and different
> -- numbers of arguments. While not technically wrong, we have a project policy
> -- to avoid this because it opens the door for confusion in connection with
> -- ORDER BY: novices frequently put the ORDER BY in the wrong place.
> -- See the fate of the single-argument form of string_agg() for history.
>
> So my vote is for a separate function and no optional arguments.
>
>

You mean like row_to_json_no_nulls() and json_agg_no_nulls()?

cheers

andrew