Re: json casts

On 5/28/14, 6:48 PM, Andrew Dunstan wrote:
> 
> On 05/27/2014 07:25 PM, Andrew Dunstan wrote:
>>
>> On 05/27/2014 07:17 PM, Tom Lane wrote:
>>> Stephen Frost <sfrost@snowman.net> writes:
>>>> * Andrew Dunstan (andrew@dunslane.net) wrote:
>>>>> Given that this would be a hard coded behaviour change, is it too
>>>>> late to do this for 9.4?
>>>> No, for my 2c.
>>> If we do it by adding casts then it'd require an initdb, so I'd vote
>>> against that for 9.4.  If we just change behavior in json.c then that
>>> objection doesn't apply, so I wouldn't complain.
>>>
>>>
>>
>>
>> I wasn't proposing to add a cast, just to allow users to add one if
>> they wanted. But I'm quite happy to go with special-casing timestamps,
>> and leave the larger question for another time.
>>
>>
> 
> 
> Here's a draft patch. I'm still checking to see if there are other
> places that need to be fixed, but I think this has the main one.

This was solved back in the day for the xml type, which has essentially
the same requirement, by adding an ISO-8601-compatible output option to
EncodeDateTime().  See map_sql_value_to_xml_value() in xml.c.  You ought
to be able to reuse that.  Seems easier than routing through to_char().