MySQL内核革新：智能拦截全表扫描，百度智能云守护数据库性能与安全

Core Viewpoint - The article discusses the implementation of a dynamic control mechanism for full table scans in Baidu's intelligent cloud database, aimed at preventing performance issues caused by inefficient SQL queries in large-scale production environments [1][17]. Group 1: Mechanism Overview - Full table scans are identified as a common performance killer in database operations, particularly in environments with large data volumes [1]. - Baidu's intelligent cloud database has developed a mechanism for real-time detection, interception, and alerting of inefficient SQL queries [1][17]. - The mechanism includes two operational modes: interception mode, which blocks full table scans, and alert mode, which allows execution but logs the SQL for monitoring [1][2]. Group 2: Control Variables - Two system variables are introduced to manage full table scan behavior: - gaia_prevent_full_table_scans (default OFF) which, when enabled, throws an error for full table scans [1][2]. - gaia_full_table_scans_alarm_allowed (default ON) which logs warnings for executed full table scans without blocking them [2][4]. Group 3: Implementation Details - The mechanism is integrated at the kernel level of MySQL, ensuring deep integration without the need for external scripts or middleware [3]. - The interception logic is designed to throw an error and interrupt execution if a full table scan is detected while gaia_prevent_full_table_scans is ON [4]. - The alert logic records the SQL in logs when a full table scan occurs while gaia_full_table_scans_alarm_allowed is ON [4][11]. Group 4: Testing and Results - The mechanism has been validated across various scenarios, confirming that normal indexed queries proceed without issues, while full table scans are accurately intercepted in interception mode [11][12]. - System library queries remain unaffected by the full table scan controls, ensuring internal operations are not disrupted [13][14]. - In cases where both control variables are OFF, full table scans are allowed without alerts, while both being ON prioritizes interception [15][16]. Group 5: Benefits - The full table scan control mechanism provides immediate benefits, including risk prevention, visibility into inefficient SQL, flexible scheduling, and seamless integration [17]. - This tool is particularly valuable for enterprises with medium to large-scale MySQL clusters, enhancing database reliability and operational efficiency [17].