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 In this article, we are going to see how to implement a non-trivial consistency check using a PostgreSQL INSERT and UPDATE trigger. By using a database trigger after executing an INSERT or UPDATE, we can ensure that the sum of salaries in a given department does not exceed the maximum budget allocated for the given department.
Introduction In this article, we are going to see how a deadlock can occur in a relational database system, and how Oracle, SQL Server, PostgreSQL, or MySQL recover from a deadlock situation.
Introduction Ever wanted to connect to a relational database using Java and didn’t know which JDBC Driver Maven dependency to use? If so, this article is surely going to help you from now on.
Introduction In this article, we are going to discuss several data pagination best and worst practices. Data pagination is omnipresent in enterprise applications. Yet, most solutions, not only they offer a bad user experience, but they are also inefficient.
Introduction In a relational database, a relationship is formed by correlating rows belonging to different tables. A table relationship is established when a child table defines a Foreign Key column that references the Primary Key column of its parent table. Every database table relationship is, therefore, built on top of Foreign Key columns, and there can be three table relationship types: one-to-many is the most common relationship, and it associates a row from a parent table to multiple rows in a child table. one-to-one requires the child table Primary Key to be… Read More
Introduction In this article, we are going to see how we can implement a database job queue using SKIP LOCKED. I decided to write this article while answering this Stack Overflow question asked by Rafael Winterhalter. Since SKIP LOCKED is a lesser-known SQL feature, it’s a good opportunity to show you how to use it and why you should employ it, especially when implementing a job queue task.
Introduction In this article, we are going to see how a relational database executes SQL statements and prepared statements.
Introduction In this article, I’m going to show you how you can log the database transaction id associated with a given SQL statement using the MDC (Mapped Diagnostic Context) feature offered by many logging frameworks. If you are writing data access code, you have to use logging. As I explained in this article, using a JDBC proxy tool like datasource-proxy or p6spy is the best approach to logging SQL statements. With datasource-proxy, you can easily build a JUnit extension to automatically detect N+1 query issues. For more details, check out the db-util… Read More
Introduction In software terminology, multitenancy is an architectural pattern which allows you to isolate customers even if they are using the same hardware or software components. Multitenancy has become even more attractive with the widespread adoption of cloud computing. A relational database system provides a hierarchy structure of objects which, typically, looks like this: catalog -> schema -> table. In this article, we are going to see how we can use each of these database object structures to accommodate a multitenancy architecture.