Introduction In this article, we are going to see how SQL Server Foreign Key constraints are locking the parent record when executing a child record UPDATE. This situation is specific to SQL Server and happens even when using the Read Committed Snapshot Isolation level.
Introduction The 2PL (Two-Phase Locking) algorithm is one of the oldest concurrency control mechanisms used by relational database systems to guarantee data integrity. In this article, I’m going to explain how the 2PL algorithm works and how you can implement it in any programming language.
Introduction Last week, Burkhard Graves asked me to answer the following StackOverflow question: And, since he wasn’t convinced about my answer: I decided to turn it into a dedicated article and explain how UPSERT and MERGE work in the top 4 most common relational database systems: Oracle, SQL Server, PostgreSQL, and MySQL.
Introduction PostgreSQL, like many modern RDBMS, offers both MVCC (Multi-Version Concurrency Control) and explicit pessimistic locking for various use cases when you want a custom concurrency control mechanism. However, PostgreSQL also offers advisory locks which are very convenient to implement application-level concurrency control patterns. In this article, we are going to explain how PostgreSQL advisory locks work and how you should use them.