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Add gap lock based transactional statement detection for InnoDB - #26

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akshaysuryawanshi wants to merge 2 commits into
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PS-10098-gap-lock-502
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Add gap lock based transactional statement detection for InnoDB#26
akshaysuryawanshi wants to merge 2 commits into
release-8.4.5-501from
PS-10098-gap-lock-502

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@akshaysuryawanshi akshaysuryawanshi commented Oct 1, 2025

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Adding gap lock based query detection for InnoDB. This will be useful in CI.

@akshaysuryawanshi akshaysuryawanshi self-assigned this Oct 1, 2025
@akshaysuryawanshi akshaysuryawanshi changed the title Ps 10098 gap lock 502 Add gap lock based transactional statement detection for InnoDB Oct 1, 2025
@akshaysuryawanshi

akshaysuryawanshi commented Oct 2, 2025

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Testing,

Testing the gap lock detection functionality,

Setup,

mysql> CREATE DATABASE IF NOT EXISTS gap_test;
Query OK, 1 row affected (0.02 sec)

mysql> USE gap_test;
Database changed
mysql> DROP TABLE IF EXISTS test_innodb;
Query OK, 0 rows affected, 1 warning (0.02 sec)

mysql> CREATE TABLE test_innodb (
    ->     id INT PRIMARY KEY,
    ->     name VARCHAR(50),
    ->     age INT,
    ->     INDEX idx_age (age)
    -> ) ENGINE=InnoDB;
Query OK, 0 rows affected (0.05 sec)

mysql> INSERT INTO test_innodb VALUES
    ->     (1, 'Alice', 25),
    ->     (5, 'Bob', 30),
    ->     (10, 'Charlie', 35),
    ->     (15, 'David', 40),
    ->     (20, 'Eve', 45);
Query OK, 5 rows affected (0.03 sec)
Records: 5  Duplicates: 0  Warnings: 0

Test 1: gap_lock_raise_error=off and innodb_detect_gap_lock_usage=off

mysql> SELECT * FROM test_innodb;
+----+---------+------+
| id | name    | age  |
+----+---------+------+
|  1 | Alice   |   25 |
|  5 | Bob     |   30 |
| 10 | Charlie |   35 |
| 15 | David   |   40 |
| 20 | Eve     |   45 |
+----+---------+------+
5 rows in set (0.01 sec)

mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE id BETWEEN 2 AND 8 FOR UPDATE;
+----+------+------+
| id | name | age  |
+----+------+------+
|  5 | Bob  |   30 |
+----+------+------+
1 row in set (0.01 sec)

mysql> SHOW WARNINGS;
Empty set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE id BETWEEN 21 AND 29 FOR UPDATE;
Empty set (0.00 sec)

mysql> SHOW WARNINGS;
Empty set (0.01 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE age BETWEEN 28 AND 33 FOR UPDATE;
+----+------+------+
| id | name | age  |
+----+------+------+
|  5 | Bob  |   30 |
+----+------+------+
1 row in set (0.00 sec)

mysql> SHOW WARNINGS;
Empty set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE id > 10 AND id < 20 FOR UPDATE;
+----+-------+------+
| id | name  | age  |
+----+-------+------+
| 15 | David |   40 |
+----+-------+------+
1 row in set (0.01 sec)

mysql> SHOW WARNINGS;
Empty set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE id = 7 FOR UPDATE;
Empty set (0.00 sec)

mysql> SHOW WARNINGS;
Empty set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.01 sec)

Test 2: gap_lock_raise_error=warning and innodb_detect_gap_lock_usage=on

mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE id BETWEEN 2 AND 8 FOR UPDATE;
+----+------+------+
| id | name | age  |
+----+------+------+
|  5 | Bob  |   30 |
+----+------+------+
1 row in set, 1 warning (0.00 sec)

mysql> SHOW WARNINGS;
+---------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                                                                                                                                                                                                                                                                                                                                                                                                |
+---------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Warning | 8020 | Using Gap Lock without full unique key in multi-table or multi-statement transactions is not allowed. You need to either 1: Execute 'SET SESSION gap_lock_raise_error=off' if you are sure that your application does not rely on Gap Lock. 2: Rewrite queries to use all unique key columns in WHERE equal conditions. 3: Rewrite to single-table, single-statement transaction. Query: SELECT * FROM test_innodb WHERE id BETWEEN 2 AND 8 FOR UPDATE |
+---------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE id BETWEEN 21 AND 29 FOR UPDATE;
Empty set, 1 warning (0.00 sec)

mysql> SHOW WARNINGS;
+---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
+---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Warning | 8020 | Using Gap Lock without full unique key in multi-table or multi-statement transactions is not allowed. You need to either 1: Execute 'SET SESSION gap_lock_raise_error=off' if you are sure that your application does not rely on Gap Lock. 2: Rewrite queries to use all unique key columns in WHERE equal conditions. 3: Rewrite to single-table, single-statement transaction. Query: SELECT * FROM test_innodb WHERE id BETWEEN 21 AND 29 FOR UPDATE |
+---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> START TRANSACTION;
Query OK, 0 rows affected (0.01 sec)

mysql> SELECT * FROM test_innodb WHERE age BETWEEN 28 AND 33 FOR UPDATE;
+----+------+------+
| id | name | age  |
+----+------+------+
|  5 | Bob  |   30 |
+----+------+------+
1 row in set, 1 warning (0.00 sec)

mysql> SHOW WARNINGS;
+---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
+---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Warning | 8020 | Using Gap Lock without full unique key in multi-table or multi-statement transactions is not allowed. You need to either 1: Execute 'SET SESSION gap_lock_raise_error=off' if you are sure that your application does not rely on Gap Lock. 2: Rewrite queries to use all unique key columns in WHERE equal conditions. 3: Rewrite to single-table, single-statement transaction. Query: SELECT * FROM test_innodb WHERE age BETWEEN 28 AND 33 FOR UPDATE |
+---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE id > 10 AND id < 20 FOR UPDATE;
+----+-------+------+
| id | name  | age  |
+----+-------+------+
| 15 | David |   40 |
+----+-------+------+
1 row in set, 1 warning (0.00 sec)

mysql> SHOW WARNINGS;
+---------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
+---------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Warning | 8020 | Using Gap Lock without full unique key in multi-table or multi-statement transactions is not allowed. You need to either 1: Execute 'SET SESSION gap_lock_raise_error=off' if you are sure that your application does not rely on Gap Lock. 2: Rewrite queries to use all unique key columns in WHERE equal conditions. 3: Rewrite to single-table, single-statement transaction. Query: SELECT * FROM test_innodb WHERE id > 10 AND id < 20 FOR UPDATE |
+---------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE id = 7 FOR UPDATE;
Empty set (0.00 sec)

mysql> SHOW WARNINGS;
Empty set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

Test 3: gap_lock_raise_error=error

mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * FROM test_innodb WHERE id BETWEEN 2 AND 8 FOR UPDATE;
ERROR 1105 (HY000): Using Gap Lock without full unique key in multi-table or multi-statement transactions is not allowed. You need to either 1: Execute 'SET SESSION gap_lock_raise_error=off' if you are sure that your application does not rely on Gap Lock. 2: Rewrite queries to use all unique key columns in WHERE equal conditions. 3: Rewrite to single-table, single-statement transaction. Query: SELECT * FROM test_innodb WHERE id BETWEEN 2 AND 8 FOR UPDATE
mysql> SHOW WARNINGS;
+-------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                                                                                                                                                                                                                                                                                                                                                                                |
+-------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Error | 1105 | Using Gap Lock without full unique key in multi-table or multi-statement transactions is not allowed. You need to either 1: Execute 'SET SESSION gap_lock_raise_error=off' if you are sure that your application does not rely on Gap Lock. 2: Rewrite queries to use all unique key columns in WHERE equal conditions. 3: Rewrite to single-table, single-statement transaction. Query: SELECT * FROM test_innodb WHERE id BETWEEN 2 AND 8 FOR UPDATE |
| Error | 1213 | Deadlock found when trying to get lock; try restarting transaction                                                                                                                                                                                                                                                                                                                                                                                     |
+-------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

mysql> ROLLBACK;
Query OK, 0 rows affected (0.00 sec)

@akshaysuryawanshi
akshaysuryawanshi force-pushed the PS-10098-gap-lock-502 branch 2 times, most recently from 1e9f49d to d3570b9 Compare October 3, 2025 20:30
@akshaysuryawanshi
Add InnoDB gap lock usage detection capability
07754f8 
- Added innodb_detect_gap_lock_usage session variable
- When enabled, InnoDB reports no gap lock support to trigger detection
- Works with gap_lock_raise_error to warn/error on gap lock usage
- Useful for CI testing and migration planning from InnoDB to RocksDB
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