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How to Fix MySQL Database Error “Incorrect Key File for Table”

Summary: This blog discusses the MySQL error 'Incorrect Key File for Table' in detail. It describes possible causes behind the error and solutions to fix them. To fix the error caused due to corrupted tables, try using Stellar Repair for MySQL software. Use the software's demo version to repair the database and its corrupt tables, and preview the recoverable tables to check data integrity.


How to Fix MySQL Database Error “Incorrect Key File for Table”

You may encounter the MySQL error ‘Incorrect Key File for Table’ when running a large MySQL query. For instance, some users have reported receiving the error while executing a query to fetch thousands of records from a table using more than one JOIN.

Why Does MySQL Return ‘Incorrect Key File for Table’ Error When Running a Query?

The complete MySQL error message “Incorrect key file for table ‘FILEPATH.MYI’; try to repair it” suggests that you can try to repair the key. Looking at your table FILEPATH can help you find more details about the error:

  • If the FILEPATH looks similar to ‘/tmp/#sql_xxxx.MYI‘, it means that your query is returning a large result set. The/tmp folder used for storing a temporary table containing the larger result set is too small for the query size. Essentially, there is not sufficient space in your /tmp folder for the temporary table.
  • If your FILEPATH contains the database table’s name, it’s likely that your table is corrupt.

Possible Causes Behind MySQL Error’ Incorrect Key File for Table’ and Their Solutions

You may be getting the error because of a disk space issue or corruption in MySQL table. Read on to know how you can resolve these two issues.

Cause 1 – Insufficient Disk Space in the Temporary Folder (/Tmp)

Note: You won’t get the error on executing individual queries, but you may encounter the error when running large queries simultaneously on the same MySQL Server.

The primary reason that results in MySQL ‘Incorrect key file’ error is that your query is fetching data greater than the size of your /tmp folder (i.e., the folder used for storing temporary tables).

Solution – Change the location of ‘/temp’ folder

First of all, you must determine if the disk partition is full by looking at your /tmp folder size. Run the df command with ‘-h‘ option to check disk usage of the file system in human-readable form:

df –h

If the partition is full, then change the location of the /tmp folder to a disk with ample free space. Change the file location in the MySQL configuration file (.cnf).

Sometimes, the /tmp folder is big enough, but it might still get full. In that case, you will need to clean up some space in the folder manually.

Cause 2 – Corrupted Keys or Table

Table corruption is another reason that may lead to the ‘Incorrect Key File for Table’ error.

Solution – Re-create or Repair the Corrupted Table

To resolve the issue, drop/re-create the corrupt table and then re-insert the data.

For example, in the following query ‘DELETE’ operation is used for dropping the table, and ‘OPTIMIZE’ TABLE command is used afterward to free disk space.

mysql> DELETE tbl_name WHERE id < 200000;

mysql> OPTIMIZE TABLE tbl_name;

If you cannot re-insert the data, try repairing the table. For MyISAM tables, you can use the ‘REPAIR table’ command to fix the corruption:

REPAIR TABLE tbl_name USE_FRM;

This command will work only on MyISAM tables. For repairing tables with InnoDB database engine, check out the best ways to repair InnoDB table corruption in MySQL. But, running a repair command for each of the tables in the query can be a lengthy and time-consuming process.

What Else You Can Do to Repair Corrupt Tables?

Use Stellar Repair for MySQL software to repair corrupt tables. The software helps repair MySQL database and all its objects quickly in just a few clicks. It recovers all data from the corrupted database without data loss.

Conclusion

When you encounter the MySQL error ‘Incorrect Key File for Table’, the first thing you should do is to check the location of /tmp folder to ensure that it has enough disk space to store temporary tables. If not, then change the folder location to a disk having ample free space. If there is no issue with disk space, chances are that your database table is corrupt and needs to be repaired. If you fail to repair the table manually, using MySQL database repair software can help.

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