How to Troubleshoot the Unknown Table ‘column_statistics’ in Information Schema

How to Troubleshoot the Unknown Table ‘column_statistics’ in Information Schema

As a database administrator, you may encounter different error messages in MySQL. One such error message that you may come across is the ‘Unknown table ‘column_statistics’ in information schema’ error. If you’ve encountered this error message, fret not, as we’ve got you covered. In this article, we’ll take an in-depth look at this issue and offer viable solutions to fix it.

What is the Issue?

Typically, the ‘Unknown table ‘column_statistics’ in information schema’ error occurs when queries are run against the MySQL database. This error message is an indication that the column_statistics table is missing from the information schema database.

The information schema database on MySQL is a virtual database that holds metadata about your MySQL server. It contains information about the tables, columns, indexes, privileges, and more. The column_statistics table within the information schema database stores statistical data on every column in each table.

When this table is missing, you’ll likely experience some issues with your query performance.

Possible Causes of the Error

There could be several reasons why the column_statistics table is missing from the information schema database. Two of the most common reasons are:

• The table was accidentally deleted
• The table was never created during the initial server setup

How to Fix the Issue

Here are a few solutions you can try to resolve the ‘Unknown table ‘column_statistics’ in information schema’ error:

Create the column_statistics table

The easiest and most straightforward solution to fix this error is to create the missing column_statistics table. You can use the script below to create the necessary table:

CREATE TABLE `column_statistics` (
  `db_name` char(64) NOT NULL DEFAULT '',
  `table_name` char(64) NOT NULL DEFAULT '',
  `column_name` char(64) NOT NULL DEFAULT '',
  `histogram` blob,
  `nulls_ratio` double DEFAULT NULL,
  `avg_length` double DEFAULT NULL,
  `max_length` bigint(20) DEFAULT NULL,
  `cardinality` bigint(20) DEFAULT NULL,
  PRIMARY KEY (`db_name`,`table_name`,`column_name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 STATS_PERSISTENT=0;

Restore the Missing Table

If you have a recent backup of your MySQL server, you can try restoring the missing table from the backup. To restore the table, follow these steps:

1. Stop the MySQL server
2. Restore the information schema database from the backup
3. Start the MySQL server

Upgrade MySQL Server

Another solution is to upgrade the MySQL server to a version that supports the column_statistics table. This solution is best if you’re using an older version of MySQL that doesn’t include the table. Upgrading to a newer version will likely resolve the error.

Conclusion

In conclusion, encountering the ‘Unknown table ‘column_statistics’ in information schema’ error is quite common in MySQL. However, with the solutions mentioned above, you should be able to resolve the issue quickly. Remember to always have a backup of your MySQL server in case of any unforeseen issues.

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