[HACKERS] Jsonb transform for pl/python

Hi.
I've implemented jsonb transform
(https://www.postgresql.org/docs/9.5/static/sql-createtransform.html)
for pl/python. 

1. '{"1":1}'::jsonb is transformed into dict {"1"=>1}, while
'["1",2]'::jsonb is transformed into list(not tuple!) ["1", 2]

2. If there is a numeric value appear in jsonb, it will be transformed
to decimal through string (Numeric->String->Decimal). Not the best
solution, but as far as I understand this is usual practise in
postgresql to serialize Numerics and de-serialize them.

3. Decimal is transformed into jsonb through string
(Decimal->String->Numeric).

An example may also be helpful to understand extension. So, as an
example, function "test" transforms incoming jsonb into python,
transforms it back into jsonb and returns it.

create extension jsonb_plpython2u cascade;

create or replace function test(val jsonb)
returns jsonb
transform for type jsonb
language plpython2u
as $$
return (val);
$$;

select test('{"1":1,"example": null}'::jsonb);

--
Anthony Bykov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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