📋

Description

This error occurs when you attempt to define or alter a database field (column) with a comment that exceeds MySQL's maximum allowed length. The error message will specify the exact maximum length in bytes permitted for field comments.

💬

Error Message

Comment for field '%s' is too long (max = %lu)

🔍

Known Causes

3 known causes

⚠️

Excessive Comment Length

The comment string provided for a database field directly surpasses the maximum byte length MySQL permits for column comments.

⚠️

Automated Schema Generation

An ORM, schema migration tool, or other automated process generated a field comment that is longer than MySQL's limit when applied.

⚠️

Migration from Other Systems

Importing a database schema from a system that supports longer field comments into MySQL can trigger this error.

🛠️

Solutions

3 solutions available

1. Shorten the Field Comment easy

Reduce the length of the comment associated with the specific column.

1

Identify the field causing the error. The error message usually specifies the field name (e.g., '%s').

2

Edit the `ALTER TABLE` or `CREATE TABLE` statement that is failing and shorten the `COMMENT` string for that specific field to be within the allowed limit (typically 1024 characters in recent MySQL versions, but can vary).

ALTER TABLE your_table_name MODIFY COLUMN your_column_name VARCHAR(255) COMMENT 'This is a shortened comment.';

3

Re-run the modified SQL statement.

2. Remove the Field Comment Entirely easy

Delete the comment from the column definition if it's not strictly necessary.

1

Locate the `ALTER TABLE` or `CREATE TABLE` statement that is generating the error.

2

Remove the `COMMENT '...'` clause for the problematic column.

ALTER TABLE your_table_name MODIFY COLUMN your_column_name VARCHAR(255);

3

Execute the modified SQL statement.

3. Increase the `innodb_large_prefix` and `innodb_file_format` for Older MySQL Versions medium

For older MySQL versions where comments might be limited by table format, enabling large prefixes can help.

1

Check your MySQL version. This solution is primarily for older versions (e.g., before 5.6) where `innodb_large_prefix` and `innodb_file_format` might influence column comment limits.

SELECT VERSION();

2

Edit your MySQL configuration file (e.g., `my.cnf` or `my.ini`).

3

Under the `[mysqld]` section, add or modify the following parameters:

[mysqld]
innodb_file_format = Barracuda
innodb_file_per_table = ON
innodb_large_prefix = ON

4

Restart your MySQL server for the changes to take effect.

sudo systemctl restart mysql  # Or your system's equivalent command

5

Re-run the `ALTER TABLE` or `CREATE TABLE` statement.

🔗

Related Errors

5 related errors

MySQL Error 1629: Field Comment Too Long