Re: Calling json_* functions with JSONB data

On Mon, May 23, 2016 at 11:14 AM, David G. Johnston <
david(dot)g(dot)johnston(at)gmail(dot)com> wrote:

> On Mon, May 23, 2016 at 12:55 PM, Peter van Hardenberg <pvh(at)pvh(dot)ca> wrote:
>
>> Hi there,
>>
>> I noticed it was very easy to accidentally call the json_* form of JSON
>> manipulation functions with jsonb data as input. This is pretty
>> sub-optimal, since it involves rendering the jsonb then reparsing it and
>> calling the json_* form of the function.
>>
>> Fortunately, this seems quite easy to resolve by taking advantage of our
>> ability to add json_*(jsonb) form of the functions.
>>
>> I talked this over with Andrew who had no objections and suggested I
>> float it on the list before writing a patch. Looks pretty straightforward,
>> just a few new data rows in pg_proc.h.
>>
>> Anyone have any concerns or suggestions?
>>
>>
> Please provide an example of what you are talking about.
>
> SELECT json_array_length('[1,2]'::jsonb)
> ERROR: function json_array_length(jsonb) does not exist
>
> -- The function name is "jsonb_array_length"; and there is no implicit
> cast between the two.
>

He is saying that he accidentally calls json_array_length() instead of
jsonb_array_length()
and that it is an annoying usability problem. It happens to me too and I
agree it would be better if you could just call json_array_length()
regardless if the type is JSON or JSONB. If there is some significant
functionality difference from the user's perspective then having separate
"json_" and "jsonb_" functions makes sense, but in your example there is
not.