The following documentation comment has been logged on the website: Page: https://www.postgresql.org/docs/17/functions-json.html Description:
On the manual page https://www.postgresql.org/docs/current/functions-json.html, in the Table 9.48. "SQL/JSON Testing Functions" there is a description of IS JSON. It includes the next sentence: "If WITH UNIQUE KEYS is specified, then any object in the expression is also tested to see if it has duplicate keys." And such text is ambiguous, because the term "object" has certain meaning regarding json format. In reality the option WITH UNIQUE KEYS allows to check for duplicated keys any array element not object. For objects, both WITH UNIQUE KEYS and WITHOUT UNIQUE KEYS return false, and both IS JSON ARRAY WITH UNIQUE KEY and IS JSON ARRAY WITHOUT UNIQUE KEY return true (it is at the same time with and without unique values, how it is possible?), i.e. it works the same as just IS JSON ARRAY. The example code that confirms my reasoning: SELECT js.vl AS "tested str", js.vl IS JSON OBJECT WITH UNIQUE KEYS AS ".. object w. UQ keys", js.vl IS JSON OBJECT WITHOUT UNIQUE KEYS AS ".. object w/o UQ keys", js.vl IS JSON ARRAY WITH UNIQUE KEYS AS ".. array w. UQ keys", js.vl IS JSON ARRAY WITHOUT UNIQUE KEYS AS ".. array w/o UQ keys", js.vl IS JSON ARRAY ".. array" FROM (VALUES ('{{"a": "a1"}, {"a": "a2"}}'), ('[{"a": "a1"}, {"a": "a2"}]'), ('["a", "a"]')) AS js(vl); I'm not sure what should be the right logic for this option, for me it looks now the same as simple IS JSON ARRAY without any UNIQUE KEY option, but if we use an option it should be either true for WITH UNIQUE KEYS or WITHOUT UNIQUE KEYS but not for both at the same time. But anyway the sentence I showed above should contain "array" instead of "object" because for objects it returns false independently of applied option. I tested it on "PostgreSQL 17.0 on x86_64-windows, compiled by msvc-19.41.34120, 64-bit".
