The common type of bigint and bigint unsigned is not stable in TiDB

[windtalker]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

mysql> create table test(id int, col_bigint bigint, col_unsigned_bigint bigint unsigned);                                                                                                Query OK, 0 rows affected (0.09 sec)

mysql> insert into test values(1,-1,18446744073709551614);                                                                                                                               Query OK, 1 row affected (0.01 sec)

mysql> select case when id = 1 then col_unsigned_bigint else col_bigint end c1 from  test;
+----------------------+
| c1                   |
+----------------------+
| 18446744073709551614 |
+----------------------+
1 row in set (0.01 sec)

mysql> select case when id = 2 then col_bigint else col_unsigned_bigint end c2 from  test;
+----+
| c2 |
+----+
| -2 |
+----+
1 row in set (0.00 sec)

2. What did you expect to see?

the above two sql should return the same result(The same query in Mysql-5.7 return -2)

3. What did you see instead?

the first one's return type is bigint unsigned, and the second one's return type is bigint

4. What version of TiDB are you using? (tidb-server -V or run select tidb_version(); on TiDB)

TiDB master

[rebelice]

Both SQL will return the same result (18446744073709551614) on the master, related PR #21062 .
On the other hand, the above two SQL return the 18446744073709551614 in MySQL-8.0, so I think this issue has been resolved, and we should close it.

[ti-srebot]

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Not a bug

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Bug

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1. Root Cause Analysis (RCA) (optional)

2. Symptom (optional)

3. All Trigger Conditions (optional)

4. Workaround (optional)

5. Affected versions

6. Fixed versions

[rebelice]

close by #21062, cherry-pick release-4.0 PR is #21236

[rebelice]

Please edit this comment to complete the following information

Bug

Note: Make Sure that 'component', and 'severity' labels are added

1. Root Cause Analysis (RCA)

Not process UnsignedFlag in AggFieldType

2. Symptom

Wrong result when using unsigned in AggField

3. All Trigger Conditions

• using unsigned in AggField

4. Workaround (optional)

5. Affected versions

[v4.0.1:v4.0.8]

6. Fixed versions

v4.0.9