Why Does My MySQL Application Throw a \'Prepared Statement Needs to Be Re-prepared\' Fatal Error?

Troubleshooting MySQL Fatal Error: "Prepared Statement Needs to Be Re-prepared"

In a recent migration to a hosting server, a user encountered a persistent fatal error when accessing a website with MySQL Stored Procedures. The error message indicated that the prepared statement required re-preparation.

Investigating the Issue

The error "Prepared statement needs to be re-prepared" suggests a discrepancy between the local and server environments. It could originate from various reasons, including:

• MySQL configuration settings
• Incompatible database versions
• Query or connection issues

Solution: Adjusting MySQL Configuration

After eliminating other potential causes, the issue was traced to a known MySQL bug (#42041). The suggested solution is to increase the value of the table_definition_cache setting.

The table_definition_cache determines the number of table definitions that MySQL caches in memory. A low value can cause the server to re-prepare prepared statements if it encounters a table with an updated definition.

Updating MySQL Configuration

To adjust the table_definition_cache setting, follow these steps:

1. Edit the MySQL my.cnf configuration file.

2. Add or modify the following line:

   table_definition_cache=<new_value>

   Where is a larger value, such as 4096 or 8192.

3. Restart the MySQL service.

Additional Considerations

Statement caching can also be affected by other factors, such as:

• The MySQL max_statement_cache_size setting, which controls the maximum amount of memory allocated for statement caching.
• The query_cache_type setting, which determines how MySQL manages query caching.

Refer to the MySQL documentation for more comprehensive information on statement caching.

By increasing the value of the table_definition_cache setting, the user in this case was able to resolve the issue and eliminate the fatal error.

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