Monthly Archives: November 2023

What I would change if I saw your database

This post briefly covers the history of databases, transaction fundamentals, and then proceeds to explain what I would change if I saw your database. It is highly-opinionated, and based on decades of experience in working with relational databases.

History

The term relational database was Invented by E. F. Codd at IBM in 1970 in his paper “A Relational Model of Data for Large Shared Data Banks.” The first commercially available RDBMS was Oracle, released in 1979 by Relational Software, now Oracle Corporation. Currently, the most popular relational databases are: Oracle, MySql, Microsoft SQL Server, PostgreSQL, DB2, SQLite, Sybase. They all use a variant of SQL. My personal favorite database is PostreSQL. It is free, open-source, and most faithfully implements ANSI-SQL.

Relational Databases Today

The relational database can provide the right persistence solution for most business needs. They are extraordinarily fast and reliable. They can manage petabyte scale data. There are plenty of tools written for them. They are simple to use. Right or wrong, they are also one of the most common enterprise integration patterns.

Continue reading →

Bad Things Happen – Recognizing Common Pitfalls in Java Concurrency Programming

The rules in concurrency programming are different. Single threaded code is easily understood as deterministic. However, deterministic rules can change when multiple threads are reading and writing to the same memory space. It has been my experience that these rules for writing deterministic thread-safe code are often misunderstood. Bad things that we never expect to happen, happen.

Concurrency programming is mostly about ensuring that your system remains deterministic when multiple threads read and write to the same memory space.

Introductory Concurrency Problem

Let’s take one of the simplest concurrency problems and I will describe what can go wrong.

Let’s say that there exist an Account object in memory with a balance of $500.00, and two threads are reading and writing to it. Thread 1 wants to add $25000 to the balance. Thread 2 wants to withdraw $300 from the balance. If the code is not thread safe, then it will be quite possible for an execution of this scenario to yield a balance of $200.00.

Continue reading →