👀 Views: 96 💬 Answers: 1 📅 Created: 2025-07-17

mysql pdo transactions innodb foreign-keys PHP

I'm experiencing a `Lock wait timeout exceeded; try restarting transaction` behavior when trying to execute a transaction that involves multiple tables with foreign key constraints. My setup includes MySQL 8.0 with the InnoDB storage engine, and I'm trying to insert a record into a child table that references a parent table. The parent and child tables are set up as follows: ```sql CREATE TABLE parent ( id INT PRIMARY KEY, name VARCHAR(255) ); CREATE TABLE child ( id INT PRIMARY KEY, parent_id INT, CONSTRAINT fk_parent FOREIGN KEY (parent_id) REFERENCES parent(id) ); ``` I start a transaction to insert a new parent and then the corresponding child record: ```php try { $pdo->beginTransaction(); // Insert into parent $stmt = $pdo->prepare("INSERT INTO parent (id, name) VALUES (?, ?)"); $stmt->execute([1, 'Parent Name']); // Insert into child $stmt = $pdo->prepare("INSERT INTO child (id, parent_id) VALUES (?, ?)"); $stmt->execute([1, 1]); $pdo->commit(); } catch (Exception $e) { $pdo->rollBack(); echo "Failed: " . $e->getMessage(); } ``` The scenario arises consistently when I run this code, and the behavior message indicates a lock wait timeout. I've checked for potential deadlocks using `SHOW ENGINE INNODB STATUS;` and there don't seem to be any obvious deadlocks. I have also tried increasing the `innodb_lock_wait_timeout` setting, but that doesn't resolve the scenario. What could be causing this lock timeout when trying to insert records with foreign keys, and how can I troubleshoot this effectively? Any help would be greatly appreciated!