Tencent's Database R&D team supports internal services such as WeChat Pay, WeChat Red Packets, Tencent Advertising, and Tencent Music, and provides external support on Tencent Cloud for TencentDB products like CynosDB, CDB, and TDSQL. This public account aims to promote and share professional database knowledge, growing together with database enthusiasts.
Database auditing involves monitoring and recording database activities to detect and prevent security breaches, with methods ranging from application layer to kernel-level implementations across different database systems.
This article explains MySQL's Metadata Lock (MDL) subsystem, describing how MDL protects metadata, the lock types and modes, the transaction‑level implementation introduced in MySQL 5.5 and refined in 5.7, the lock acquisition and release algorithms, deadlock detection mechanisms, and the lock‑free hash table used to store lock objects.
This article explains how to extend a red‑black tree with a subtree‑size counter to support O(log n) rank and selection operations, detailing the required count updates during insertion, deletion, and tree rotations, and provides complete pseudocode for left/right rotations, rank queries, and element‑by‑rank retrieval.
The article introduces the ELKB stack—a combination of Elasticsearch, Logstash, Kibana, and Beats—explaining its background, user needs, architecture, component functions, typical scenarios, and the team’s practical implementations for real‑time log and time‑series data processing.
This article explains MySQL's online DDL mechanism, detailing the copy and inplace methods, the three execution phases, the allocation and structure of row_log_t, how log entries are written during DDL, and the replay process that applies those logs to the rebuilt table.
This article explains what happens inside the Linux kernel when the rm command deletes a file on an ext4 filesystem, analyzes the relevant VFS and ext4 source code, and demonstrates how large‑file deletions can degrade I/O performance of other applications.
