This article explains MySQL InnoDB's Next-Key Lock mechanism, how it combines row and gap locks to prevent phantom reads under the REPEATABLE READ isolation level, illustrates lock ranges with examples, discusses when it degrades to row or gap locks, and highlights its advantages and potential deadlock risks.
This article examines a real‑world MySQL deadlock incident, explains the inner workings of shared, exclusive, gap, next‑key, and insert‑intention locks, and shows how concurrent delete‑then‑insert operations can saturate connection pools and degrade overall database performance.
This article explains the types of InnoDB row‑level locks—record lock, gap lock, and next‑key lock—describes how MySQL determines lock ranges based on indexing, outlines the two fundamental locking principles with associated optimizations, and provides concrete examples for primary‑key and ordinary indexes.
This article explains InnoDB's three row‑lock types, when MySQL statements acquire implicit or explicit locks, and walks through concrete examples for unique and non‑unique index queries, showing how Next‑key, Record and Gap locks are determined.
This article examines how common business operations using SELECT ... FOR UPDATE and INSERT can cause MySQL Next‑Key lock deadlocks, explains the underlying gap‑lock and row‑lock mechanisms, demonstrates practical experiments, and proposes strategies such as postponing locks or using primary‑key updates to avoid such deadlocks.
This article examines how common business operations using SELECT ... FOR UPDATE and INSERT can cause Next‑Key lock deadlocks in MySQL under repeatable‑read isolation, demonstrates the locking behavior with practical SQL examples, and proposes strategies such as post‑locking and primary‑key updates to prevent such deadlocks.
This article explains why an UPDATE on a MySQL row that changes a regular column proceeds without blocking, while an UPDATE that modifies the primary‑key value gets blocked, by analyzing the locks set by preceding transactions, the B+‑tree index structure, and the delete‑plus‑insert rewrite performed by InnoDB.
This comprehensive guide explains how MySQL's InnoDB engine applies row‑level locks—including shared, exclusive, gap, and next‑key locks—based on different SQL statements, isolation levels, and index types, and shows how to analyze and avoid phantom reads with practical experiments.
This article walks through a real MySQL deadlock scenario, explaining the four necessary deadlock conditions, illustrating how Next‑Key locks on non‑unique indexes cause gap locks, and presenting step‑by‑step analysis, experimental verification, and practical recommendations to avoid such deadlocks in production systems.
This article explains the four transaction isolation levels, defines phantom reads, and details how MySQL's InnoDB engine uses MVCC snapshot reads and next‑key locking (including the next‑key principle and lock composition) to prevent phantom reads under the REPEATABLE READ isolation level.
This article explains why phantom reads occur under MySQL's REPEATABLE READ isolation, how InnoDB uses MVCC for snapshot reads and next‑key locks for current reads, and demonstrates the mechanisms with code examples and version‑tracking diagrams.
This article explains MySQL InnoDB’s transaction locking mechanisms—including shared, exclusive, intention, gap, and next‑key locks—covers lock compatibility, demonstrates lock behavior with practical examples, explores phantom reads, lost updates, optimistic vs. pessimistic locking, and analyzes common deadlock scenarios.
This article examines MySQL InnoDB's next‑key lock behavior by creating a test table, running concurrent transactions, and analyzing how the lock range is determined across primary and secondary index columns, revealing why certain insert statements are blocked while others succeed.
