Master PostgreSQL Locking and Deadlock Prevention Techniques

This resource offers a total of 60 PostgreSQL Locking mechanisms and deadlock prevention problems for practice. It includes 12 main exercises, each accompanied by solutions, detailed explanations, and four related problems.

Following exercises illustrate various techniques for handling locks and preventing deadlocks in PostgreSQL, ensuring optimal performance and data consistency in concurrent environments.

1. Lock a Row with SELECT FOR UPDATE

Write a PostgreSQL query to lock a specific row in a table using SELECT FOR UPDATE.

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2. Lock an Entire Table Using LOCK TABLE

Write a PostgreSQL query to lock an entire table to prevent any concurrent data modifications.

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3. Use NOWAIT to Avoid Lock Waits

Write a PostgreSQL query to lock a row using SELECT FOR UPDATE with the NOWAIT option to avoid waiting if the row is already locked.

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4. Use SKIP LOCKED to Process Available Rows

Write a PostgreSQL query to lock rows using SELECT FOR UPDATE with the SKIP LOCKED option to process only unlocked rows.

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5. Simulate a Deadlock Scenario

Write a PostgreSQL query to simulate a potential deadlock by updating rows in two tables in conflicting orders.

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6. Enforce Consistent Lock Ordering

Write a PostgreSQL query to demonstrate how acquiring locks in a consistent order can prevent deadlocks.

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7. Acquire an Advisory Lock

Write a PostgreSQL query to acquire an advisory lock using pg_advisory_lock for custom application-level locking.

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8. Release an Advisory Lock

Write a PostgreSQL query to release an advisory lock acquired earlier using pg_advisory_unlock.

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9. Query System Locks Using pg_locks

Write a PostgreSQL query to display current locks in the system using the pg_locks system view.

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10. Prevent Deadlocks with Short Transactions

Write a PostgreSQL query to update a record within a short transaction to reduce the risk of deadlocks.

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11. Set a Statement Timeout to Abort Long Lock Waits

Write a PostgreSQL query to set a statement timeout that aborts queries waiting too long for locks.

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12. Test Lock Contention with pg_try_advisory_lock

Write a PostgreSQL query to test if an advisory lock can be acquired without waiting using pg_try_advisory_lock.

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More to Come !

Do not submit any solution of the above exercises at here, if you want to contribute go to the appropriate exercise page.