Re: BUG #15763: JSON nulls not handled properly

On Tuesday, April 16, 2019, PG Bug reporting form <noreply(at)postgresql(dot)org>
wrote:

> The following bug has been logged on the website:
>
> Bug reference: 15763
> Logged by: Jacob Crell
> Email address: jacobcrell(at)gmail(dot)com
> PostgreSQL version: 9.6.8
> Operating system: AWS RDS
> Description:
>
> SELECT '{"test":null}'::json->>'test' will return a null
> SELECT '{"test":null}'::json->'test' will return a string 'null'
> The 2nd option seems like it should also return a null.
>

This seems under documented but I can confidently say the behavior shown is
intended and thus not a bug. Nor should it be changed. The second example
returns a json typed value that when printed as text is the character
sequence null. It does not return a PostgreSQL string type.

Conversion of json null to PostgreSQL text results in a NULL of type text,
which is indeed the first outcome. This is, however, a lossy one-way
conversion since NULL::json is NULL, not ‘null’.

David J.