Thread: Stability of JSON textual representation

> I've noticed that when representing lists as JSON, Postgres 9.4 sometimes
> outputs spaces after commas, and other times does not.

Here is a similar test on 9.3:

# select '[1,2,3]'::json::text, '[1, 2, 3]'::json::text;
  text   |   text
---------+-----------
 [1,2,3] | [1, 2, 3]

It looks like even casting back and forth between text and json
preserves the text.

Paul

--
_________________________________
Pulchritudo splendor veritatis.

On 03/02/15 00:06, David Evans wrote:
> I've noticed that when representing lists as JSON, Postgres 9.4
> sometimes outputs spaces after commas, and other times does not.
>
>     # SELECT array_to_json(array[1, 2, 3]), json_build_array(1, 2, 3);
>
>      array_to_json | json_build_array
>     ---------------+------------------
>      [1,2,3]       | [1, 2, 3]
>
>
> This matters to me because I'm intending the hash the JSON text and
> use the hash for change detection.
>
> This difference in behaviour doesn't seem to be documented anywhere.
> Does anyone know whether it is likely to be stable?
>
> Many thanks,
>
> Dave
  Would using jsonb be more consistent?


Cheers,
Gavin

On Mon, Feb 9, 2015 at 3:07 AM, David Evans <david.evans@cantab.net> wrote:
> On 9 February 2015 at 03:57, Gavin Flower <GavinFlower@archidevsys.co.nz>
> wrote:
>>
>>  Would using jsonb be more consistent?
>
>
> Yes, casting to jsonb seems produce consistent output:
>
> # SELECT array_to_json(array[1, 2, 3])::jsonb, json_build_array(1, 2,
> 3)::jsonb;
>  array_to_json | json_build_array
> ---------------+------------------
>  [1, 2, 3]     | [1, 2, 3]
>
> That makes sense I suppose, given that only the structure in preserved in
> the jsonb representation.

This is not really due to whitespace/'structure only' preservation
aspects of json and jsonb, respectively.  What is happening here is
that the various functions that render json from text are non
consistent in terms of spacing.  Personally, I greatly prefer the
xxx_to_json functions because they don't insert spurious whitespace
making for more compact documents; putting in spaces for aesthetic
purposes is the job for a prettifier.

merlin