Re: Emitting JSON to file using COPY TO

Andrew Dunstan wrote:

> Here's a v30 set that I hope fixes these issues.

Currently there's no difference in output between the null
json value and the SQL null.

postgres=# create table tbl (j jsonb);
CREATE TABLE

postgres=# insert into tbl values('null');
INSERT 0 1

postgres=# insert into tbl values(null);
INSERT 0 1

postgres=# table tbl;
j
------
null

(2 rows)

postgres=# copy tbl to stdout with (format json);
{"j":null}
{"j":null}

If we had to reload this file, we could not determine which
kind of null we had even though they are different at the SQL
level:

postgres=# select null::jsonb is distinct from 'null'::jsonb;
?column?
----------
t

Does it have to be that way or are there valid distinct outputs
that we could use to avoid this ambiguity?

Best regards,
--
Daniel Vérité
https://postgresql.verite.pro/