This article explains how InnoDB in MySQL 8.0.32 grants table and row locks, detailing the active versus passive acquisition, the lock‑granting algorithms for tables and rows, and the priority, weight, and FIFO rules that determine lock ordering and deadlock handling.
This article explains how MySQL's SELECT ... FOR UPDATE statement acquires either row-level or table-level locks depending on the presence of indexes or primary keys, and demonstrates the behavior with multiple transaction examples and a sample table definition.
This article explains how MySQL's SELECT … FOR UPDATE statement applies different lock types—row, gap, or table—depending on whether the WHERE clause uses primary keys, unique indexes, regular indexes, range queries, or empty results, and demonstrates each case with practical SQL examples and screenshots.
This article explains how MySQL's SELECT ... FOR UPDATE statement applies different lock types—row, table, or none—depending on whether the WHERE clause uses primary keys, unique indexes, regular indexes, range queries, non‑indexed fields, or returns no rows, illustrated with practical transaction examples.
This article systematically investigates how MySQL's SELECT FOR UPDATE behaves under different versions (5.7 and 8.0) and isolation levels (RR and RC), covering twenty scenarios that vary by index type and query range, and summarizes whether the statement acquires row‑level, gap, or table‑level locks.
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 explains MySQL deadlocks through practical examples, covering lock types, exclusive vs. shared locks, lock‑in‑share‑mode vs. FOR UPDATE differences, real‑world deadlock scenarios, and multiple strategies—including isolation level tweaks, optimistic locking, and distributed locks—to prevent and resolve them.
This article experimentally verifies how SELECT FOR UPDATE behaves under different MySQL versions, isolation levels, and index conditions, revealing when it acquires row‑level, gap, or table‑level locks across 20 distinct scenarios.
This article explains how MySQL's SELECT … FOR UPDATE adds a pessimistic lock, and demonstrates that using an indexed column or primary key results in a row lock, while lacking an index causes a table lock, with step‑by‑step verification using multiple transaction examples.
When two transactions access the same data without proper coordination, concurrency bugs such as dirty reads and dirty writes can arise; the article explains these problems, the guarantees of isolation levels, and how row locks and snapshot techniques prevent them in modern databases.
This article explains how a plain SELECT does not lock data, while SELECT … FOR UPDATE adds a pessimistic lock whose scope—row or table—depends on whether the query uses an indexed or primary‑key column, and demonstrates the behavior with SQL examples and transaction scenarios.
This article explains how the SELECT ... FOR UPDATE statement in MySQL adds a pessimistic lock, describes when it results in a row lock versus a table lock based on index usage, provides verification SQL, example scenarios, and practical tips for transaction handling.
This article explains how MySQL's SELECT ... FOR UPDATE statement adds a pessimistic lock, detailing when it results in row-level locking versus table-level locking based on the presence of indexes or primary keys, and demonstrates the behavior with multiple practical examples.
This article explains how the MySQL SELECT … FOR UPDATE statement adds a pessimistic lock, why the lock type (row or table) depends on the presence of an index or primary key, and demonstrates the behavior with practical examples and SQL scripts.
This article explains how MySQL's SELECT ... FOR UPDATE statement adds pessimistic locks, detailing when it results in row‑level locks versus table‑level locks based on the presence of indexes or primary keys, and provides verification examples with code and transaction scenarios.
This article explains how MySQL implements row‑level locking, the two‑phase locking protocol, common deadlock scenarios with online ticket sales, and practical strategies—including lock ordering, deadlock detection settings and sharding tricks—to improve concurrency and reduce CPU overhead.
This article explains the differences between MySQL table locks and row locks, how they are implemented by the server and storage engines, the lock modes and types (including intention, auto‑increment, gap, next‑key, and insert‑intention locks), and provides practical SQL examples with diagrams.
This article explains the differences between MySQL table locks and row locks, describes how MyISAM and InnoDB handle locking, provides explicit lock syntax with examples, discusses gap locks, and offers practical recommendations for avoiding lock contention in concurrent applications.
This article explains MySQL shared (S) and exclusive (X) row‑level locks, demonstrates their behavior with two concurrent sessions, shows how lock ordering can cause deadlocks, and provides practical tips for using InnoDB locking correctly.
This article explains MySQL's lock mechanisms, covering table‑level, row‑level, and page locks, the differences between pessimistic and optimistic locking, shared locks, and provides guidance on when to choose table locks versus row locks in various application scenarios.
This guide explains Oracle's TX row lock mechanism, shows how to identify blocking sessions, locate the exact locked rows using system views and ROWID functions, and provides practical steps to prevent and mitigate TX lock waiting issues.
