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Subject: BUG #19737: Empty `JSON_OBJECT` cannot use documented `ON NULL` or
 unique-key clauses
To: pgsql-bugs@lists.postgresql.org
From: PG Bug reporting form <noreply@postgresql.org>
Cc: theshallow27@gmail.com
Reply-To: theshallow27@gmail.com, pgsql-bugs@lists.postgresql.org
Date: Fri, 02 Oct 2026 22:36:20 +0000
Message-ID: <19737-b44cf2e08708b613@postgresql.org>
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 <https://www.postgresql.org/message-id/19737-b44cf2e08708b613%40postgresql.org>
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The following bug has been logged on the website:

Bug reference:      19737
Logged by:          Shallow
Email address:      theshallow27@gmail.com
PostgreSQL version: 18.6
Operating system:   Linux
Description:       =20

The documented syntax makes the key/value pair list optional and says that
an
empty pair list constructs an empty object. However, adding any of the
optional
clauses without a pair causes a syntax error.

**Reproduction:**

```sql
SELECT JSON_OBJECT();                 -- returns {}
SELECT JSON_OBJECT(NULL ON NULL);     -- syntax error, SQLSTATE 42601
SELECT JSON_OBJECT(ABSENT ON NULL);   -- syntax error, SQLSTATE 42601
SELECT JSON_OBJECT(WITH UNIQUE KEYS); -- syntax error, SQLSTATE 42601
```

**Expected result:** Each form with an empty pair list should construct
`{}`;
the clauses do not change the result when there are no pairs.