Thread: BUG #17873: Empty JSONB array is ordered before all other JSONB values

The following bug has been logged on the website:

Bug reference:      17873
Logged by:          Marcus Gartner
Email address:      marcus@cockroachlabs.com
PostgreSQL version: 14.6
Operating system:   macOS 13.2.1
Description:

The JSONB Indexing documentation (here:
https://www.postgresql.org/docs/14/datatype-json.html#JSON-INDEXING) states
that:

"The btree ordering for jsonb datums is seldom of great interest, but for
completeness it is:
Object > Array > Boolean > Number > String > Null"

However, the empty JSONB array value does comply with this ordering as it is
less than all other JSONB values, as far as I
can tell.

SELECT '[]'::JSONB < j::JSONB
FROM (VALUES
  ('null'),
  ('"a"'),
  ('1'),
  ('[1]'),
  ('{}')
) v(j);
 ?column?
----------
 t
 t
 t
 t
 t
(5 rows)

Is this a bug in the B-tree ordering of JSONB values? I could not find any
notes in the source code or test cases that explain this
special case for empty JSONB arrays.

Thanks,
Marcus