“Table already exists” error when upgrading¶

Troubleshooting¶

There are several possible reasons for a duplicate table, column or key error:

• If you had previously restored your database, ensure it was restored into a completely empty database. Otherwise there will be duplicate data.
• Never use your browser’s Back button during an upgrade, as that can cause actions to run twice.
• Your server’s PHP max_execution_time may be set too low, forcing the upgrade script to end prematurely. Check with your host about increasing this value from the typical default of 30 seconds.
• If you’re using Firefox to perform the upgrade, try using Chrome or Safari instead. In some cases Firefox can re-send requests following a server error, effectively preventing the error from being seen.