MySQL operation failed: Unknown prepared statement handler (${#}) given to mysqld_stmt_execute

I have a service that has been running in production for a month with no issues. Last evening, the service failed after all queries using .execute were throwing this error. Restarting the service resolved the issue.

Let me know if I can provide more information.

[rallfo]

@dekyfin are you getting errors with your code? With manual .prepare() statement is not cached, it’s up to you to reuse it or not

Actually it does appear that manual prepare() statements are both cached and retrieved from the connection._statements LRU cache. Which is the source of the bug.

In the case of a manual .prepare() then PreparedStatementInfo.close() a CloseStatement is sent but the statement entry is not removed from the cache. Leaving an entry to the invalid prepared statement.

Replication: prepare() an insert query, execute() and close() it. Attempting to prepare() and execute() the same SQL a second time triggers this issue.

Solution:

• either stop caching manual prepare() statements
• or make PreparedStatementInfo.close() correctly delete the statement from the connection._statements cache

[xWTF]

TL;DR for anyone facing the same issue: rallfo found the exact cause of this, simply use Connection.unprepare() when you’ve done with your instead of PreparedStatementInfo.close() solves the problem. I’ve opened https://github.com/sidorares/node-mysql2/pull/1493 to address this, hopefully it clarifies the usage.