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Subject: BUG #19472: CAST(-32768::SMALLINT AS REAL) fails with "SMALLINT out of range" but -32768 is valid SMALLINT value
To: pgsql-bugs@lists.postgresql.org
From: PG Bug reporting form <noreply@postgresql.org>
Cc: vectorplanck@gmail.com
Reply-To: vectorplanck@gmail.com, pgsql-bugs@lists.postgresql.org
Date: Wed, 06 May 2026 09:09:48 +0000
Message-ID: <19472-6b130bcff370911d@postgresql.org>
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Archived-At: <https://www.postgresql.org/message-id/19472-6b130bcff370911d%40postgresql.org>
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The following bug has been logged on the website:

Bug reference:      19472
Logged by:          Pisces Mar.
Email address:      vectorplanck@gmail.com
PostgreSQL version: 17.6
Operating system:   x86_64-windows
Description:       =20

Issue Description:
When casting -32768 to SMALLINT and then to REAL using the :: operator,
PostgreSQL throws an error "smallint out of range", even though -32768 is a
valid value within the SMALLINT range (-32768 to +32767).

Steps to Reproduce:
1. Execute: SELECT CAST(-32768 :: SMALLINT AS REAL);
   Result: ERROR: SMALLINT out of range

2. Execute: SELECT CAST((-32768) :: SMALLINT AS REAL);
   Result: Successfully returns -32768

3. Execute: SELECT CAST(CAST(-32768 AS SMALLINT) AS REAL);
   Result: Successfully returns -32768

Root Cause:
The expression -32768 :: SMALLINT is being parsed as -(32768 :: SMALLINT)
instead of (-32768) :: SMALLINT. Since 32768 exceeds the maximum positive
value for SMALLINT (32767), it causes an out-of-range error.

Expected Behavior:
-32768 should be recognized as a valid SMALLINT value (the minimum value for
smallint is -32768), and the cast to REAL should succeed.

Workaround:
Use parentheses: SELECT CAST((-32768) :: SMALLINT AS REAL);
Or use standard CAST syntax: SELECT CAST(-32768 AS SMALLINT);

Environment:
PostgreSQL Version: 17.6
Operating System: x86_64-windows