Sorting Discrepancy in PostgreSQL 14.13 - Mailing list pgsql-bugs

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Your name              : minji-kim
Your email address : hzuiw33@gmail.com


# System Configuration:
---------------------
Architecture (example: Intel Pentium)                      : Intel(R) Core(TM) Ultra 7 155H
Operating System (example: Linux 2.4.18)              : VMware Workstation Pro (Ubuntu-22.04)
PostgreSQL version (example: PostgreSQL 9.6.6)  : PostgreSQL 14.13
Compiler used (example: gcc 3.3.5)                         : X (sudo apt install postgresql postgresql-contrib)


# Please enter a FULL description of your problem:
------------------------------------------------

Sorting Discrepancy in PostgreSQL 14.13

When running the following command in PostgreSQL 14.13:

```sql
CREATE TABLE t0 (c0 TEXT);
INSERT INTO t0 (c0) VALUES ('-10'), ('20'), ('-5'), ('15'), ('-25');
SELECT c0, MIN(ABS(CAST(c0 AS BIGINT))) OVER (ORDER BY c0 NULLS FIRST) AS min_function_cast FROM t0;
DROP TABLE IF EXISTS t0;
```

The result is:

```
 c0  | min_function_cast
-----+-------------------
 -10 |                10
 15  |                10
 20  |                10
 -25 |                10
 -5  |                 5
(5 rows)
```

However, in other DBMS (SQLite, MySQL, OracleDB) and PostgreSQL version 17.0, the output is:

```
 c0  | min_function_cast
-----+-------------------
 -10 |                10
 -25 |                10
 -5  |                 5
 15  |                 5
 20  |                 5
(5 rows)
```

This discrepency is due to different string sorting orders.

The minimized PoC is:

```sql
CREATE TABLE t0 (c0 TEXT);
INSERT INTO t0 (c0) VALUES ('-10'), ('20'), ('-5'), ('15'), ('-25');
SELECT c0 FROM t0 ORDER BY c0;
```

In PostgreSQL 14.13, the order is incorrect:
```
-10
15
20
-25
-5
```

While the correct order should be:

```
-10
-25
-5
10
20
```

as '-' is smaller than '1', or '2' in ascii.

I'm doubtful this is a collation issue, as most collations basically respect ASCII order.

Even if this issue appears to be related to collation, no warnings are provided when migrating from this version.

# Please describe a way to repeat the problem.  
# Please try to provide a concise reproducible example, if at all possible:
----------------------------------------------------------------------

Running the following command in PostgreSQL 14.13:

```sql
CREATE TABLE t0 (c0 TEXT);
INSERT INTO t0 (c0) VALUES ('-10'), ('20'), ('-5'), ('15'), ('-25');
SELECT c0, MIN(ABS(CAST(c0 AS BIGINT))) OVER (ORDER BY c0 NULLS FIRST) AS min_function_cast FROM t0;
DROP TABLE IF EXISTS t0;
```

Results in the incorrect sorting behavior.


If you know how this problem might be fixed, list the solution below:
---------------------------------------------------------------------
Using the correct sort criteria will solve this problem.