How to Prevent Deadlocks When Inserting Non-Existing Rows in InnoDB?

Deadlock Prevention for Inserting Non-Existent Rows in InnoDB

When attempting to insert a new row into an InnoDB database, it's essential to ensure no concurrent transactions can create the same row between the select and insert operations. This prevents race conditions and potential data corruption.

A common solution is to use a SELECT ... FOR UPDATE statement to lock on the row to be inserted. However, this method only works for existing rows. To lock on non-existent rows, a more robust approach is required.

The difficulty arises because MySQL doesn't provide a mechanism to lock non-existent records. Concurrent transactions can "lock" the same non-existent row FOR UPDATE, creating a situation where both transactions believe they have obtained a lock.

To overcome this issue, consider the following workarounds:

Semaphore Tables: Implement a semaphore table to keep track of which non-existent rows are currently being accessed. When a transaction needs to insert a new row, it first locks the corresponding semaphore, preventing other transactions from inserting the same row.

Table-Level Locking: Lock the entire table for the duration of the insert operation. This prevents any concurrent transactions from modifying the table, but it can significantly impact database performance.

By implementing proper locking mechanisms, you can guarantee the integrity of your data by preventing concurrent inserts of the same row. Consider the use of semaphore tables or table-level locking based on your specific requirements and performance considerations.

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