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Description

This error indicates that a SQL query exceeded its allowed execution time limit and was terminated by the MySQL server. It typically occurs when a query is too complex, operates on large datasets, or when the server's configured timeout is too short.

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Error Message

Query execution was interrupted, maximum statement execution time exceeded

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Known Causes

4 known causes

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Inefficient Query Design

The SQL query is poorly optimized, involves complex joins, or processes an excessively large amount of data.

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Low Statement Timeout Setting

The `max_execution_time` setting for the session or server is configured too low for the expected query workload.

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Server Resource Constraints

The MySQL server lacks sufficient CPU, memory, or I/O resources, causing queries to run slowly and hit the timeout.

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Large Data Volume

The query operates on tables with an extremely high number of rows, making even optimized queries take a long time to complete.

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Solutions

3 solutions available

1. Increase Global or Session Timeout easy

Temporarily or permanently adjust the `max_execution_time` server variable.

1

To increase the timeout for the current session only, run the following SQL command:

SET SESSION max_execution_time = 600; -- Set to 600 seconds (10 minutes), adjust as needed

2

To increase the timeout globally for all new connections (requires SUPER privilege), edit your MySQL configuration file (`my.cnf` or `my.ini`). Add or modify the `max_execution_time` parameter under the `[mysqld]` section. Restart the MySQL server for changes to take effect.

[mysqld]
max_execution_time = 600

3

Alternatively, you can set it dynamically without a restart for all new connections (requires SUPER privilege). This change will be lost on restart.

SET GLOBAL max_execution_time = 600; -- Set to 600 seconds (10 minutes), adjust as needed

2. Optimize the Slow Query medium

Analyze and rewrite the problematic SQL query to execute faster.

1

Identify the slow query. If you have the slow query log enabled, examine the log file for queries exceeding a certain threshold.

SHOW VARIABLES LIKE 'slow_query_log%';
SHOW VARIABLES LIKE 'long_query_time%';

2

Use `EXPLAIN` to analyze the query's execution plan. This will show how MySQL is accessing tables, using indexes, and performing joins.

EXPLAIN SELECT ... FROM your_table WHERE ...;

3

Based on the `EXPLAIN` output, consider the following optimizations:

1. **Add appropriate indexes:** Ensure columns used in `WHERE` clauses, `JOIN` conditions, and `ORDER BY` clauses are indexed.
2. **Rewrite the query:** Simplify complex joins, avoid `SELECT *`, use subqueries judiciously, and consider breaking down very large queries.
3. **Denormalize data:** If performance is critical and joins are a bottleneck, consider carefully denormalizing your schema (use with caution).
4. **Use appropriate data types:** Ensure data types are efficient for the data they store.

3. Review and Optimize Database Schema and Indexes advanced

Ensure your database structure and indexes are efficient for your workload.

1

Regularly analyze your database schema for potential improvements. Look for unindexed columns, redundant indexes, or inefficient data types.

SHOW INDEX FROM your_table;

2

Identify tables with high read/write activity and ensure they have appropriate indexes. Use tools like `pt-duplicate-key-checker` from Percona Toolkit to find redundant or unused indexes.

pt-duplicate-key-checker --host=<host> --user=<user> --password=<password>

3

Consider partitioning large tables if queries often filter on a specific range of data (e.g., date). This can significantly improve query performance by allowing MySQL to scan only relevant partitions.

ALTER TABLE your_table PARTITION BY RANGE (TO_DAYS(your_date_column)) (
    PARTITION p0 VALUES LESS THAN (TO_DAYS('2023-01-01')),
    PARTITION p1 VALUES LESS THAN (TO_DAYS('2024-01-01'))
);

4

Ensure your primary keys and foreign keys are correctly defined and indexed. This is crucial for maintaining data integrity and optimizing join operations.

ALTER TABLE your_table ADD PRIMARY KEY (id);
ALTER TABLE your_table ADD CONSTRAINT fk_user FOREIGN KEY (user_id) REFERENCES users(id);

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Related Errors

5 related errors

MySQL Error 3024: Query Execution Timeout