This patch intrdocuces the SQL standard IS JSON predicate. It operates
on text and bytea values representing JSON as well as on the json and
jsonb types. Each test has an IS and IS NOT variant. The tests are:
IS JSON [VALUE]
IS JSON ARRAY
IS JSON OBJECT
IS JSON SCALAR
IS JSON WITH | WITHOUT UNIQUE KEYS
These are mostly self-explanatory, but note that IS JSON WITHOUT UNIQUE
KEYS is true whenever IS JSON is true, and IS JSON WITH UNIQUE KEYS is
true whenever IS JSON is true except it IS JSON OBJECT is true and there
are duplicate keys (which is never the case when applied to jsonb values).
Nikita Glukhov
Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.
Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
{"a": 1, "b": null} | t | f | t | t | f | f | t | t
{"a": null} | t | f | t | t | f | f | t | t
{"a": 1, "b": [{"a": 1}, {"a": 2}]} | t | f | t | t | f | f | t | t
{"a": 1, "b": [{"a": 2, "b": 0}]} | t | f | t | t | f | f | t | t
(11 rows)
-- Test IS JSON deparsing
EXPLAIN (VERBOSE, COSTS OFF)
SELECT '1' IS JSON AS "any", ('1' || i) IS JSON SCALAR AS "scalar", '[]' IS NOT JSON ARRAY AS "array", '{}' IS JSON OBJECT WITH UNIQUE AS "object" FROM generate_series(1, 3) i;
Output: ('1'::text IS JSON), (('1'::text || (i)::text) IS JSON SCALAR), (NOT ('[]'::text IS JSON ARRAY)), ('{}'::text IS JSON OBJECT WITH UNIQUE KEYS)
Function Call: generate_series(1, 3)
(3 rows)
CREATE VIEW is_json_view AS
SELECT '1' IS JSON AS "any", ('1' || i) IS JSON SCALAR AS "scalar", '[]' IS NOT JSON ARRAY AS "array", '{}' IS JSON OBJECT WITH UNIQUE AS "object" FROM generate_series(1, 3) i;
\sv is_json_view
CREATE OR REPLACE VIEW public.is_json_view AS
SELECT '1'::text IS JSON AS "any",
('1'::text || i.i) IS JSON SCALAR AS scalar,
NOT '[]'::text IS JSON ARRAY AS "array",
'{}'::text IS JSON OBJECT WITH UNIQUE KEYS AS object
Andrew Dunstan
4 years ago