Python MySQL: How to Fix the \'Commands Out of Sync\' Error in Stored Procedure Calls?

Python MySQL: Resolving "Commands Out of Sync" Error

When working with MySQL stored procedures in Python via Django, issues can arise involving the synchronization of commands. This can manifest as the dreaded "commands out of sync; you can't run this command now" error when attempting to execute multiple statements within a transaction.

Understanding the Issue

By default, a cursor maintains state information across multiple executions. When calling a stored procedure, the cursor moves to a different position within the transaction. Trying to execute a subsequent SQL statement from the initial position of the cursor will result in the error.

Solution: Refreshing the Cursor

To resolve the issue, it is necessary to close the cursor and reopen it before executing any additional statements. The cursor can be closed immediately after calling fetchall() without affecting the result set.

cursor.close()

cursor = connection.cursor() 

This effectively resets the cursor's position and allows for the execution of the next SQL statement. It is important to note that the original cursor object should no longer be used after closing it.

Example

Consider the following code snippet:

cursor.callproc('my_mysql_procedure', [some_id,]) 
result = cursor.fetchall()

cursor.close() 
cursor = connection.cursor() 

cursor.execute("select * from some_table")
result = cursor.fetchall()

In this case, calling cursor.close() after fetchall() ensures that the cursor's state is reset and the subsequent execute() statement can be executed successfully.

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