Yesterday, my Danish friend, Flemming Harms, asked my a very interesting question related to when a JDBC batch update fails.
Basically, considering we are going to group several DML statements in a batch, we need a way to tell which statement is the cause of the failure. This post is going to answer this question in more detail.
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Dealing with time zones is always challenging. As a rule of thumb, it’s much easier if all date/time values are stored in the UTC format, and, if necessary, dealing with time zone conversations in the UI only.
This article is going to demonstrate how you can accomplish this task with JDBC and the awesome
hibernate.jdbc.time_zone configuration property.
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Each database application is unique. While most of the time, deleting a record is the best approach, there are times when the application requirements demand that database records should never be physically deleted.
So who uses this technique?
For instance, StackOverflow does it for all Posts (e.g. Questions and Answers). The StackOverflow
Posts table has a
ClosedDate column which acts as a soft delete mechanism since it hides an Answer for all users who have less than 10k reputation.
If you’re using Oracle, you can take advantage of its Flashback capabilities, so you don’t need to change your application code to offer such a functionality. Another option is to use the SQL Server Temporal Table feature.
However, not all relational database systems support Flashback queries, or they allow you to recover a certain record without having to restore from a database backup. In this case, Hibernate allows you to simplify the implementation of soft deletes, and this article is gong to explain the best way to implement the logical deletion mechanism.
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In Concurrency Control theory, there are two ways you can deal with conflicts:
- You can avoid them, by employing a pessimistic locking mechanism (e.g. Read/Write locks, Two-Phase Locking)
- You can allow conflicts to occur, but you need to detect them using an optimistic locking mechanism (e.g. logical clock, MVCC)
Because MVCC (Multi-Version Concurrency Control) is such a prevalent Concurrency Control technique (not only in relational database systems, in this article, I’m going to explain how it works.
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Today, one of my Twitter followers sent me the following StackOverflow question, and, while answering it, I realized that it definitely deserves a post of its own.
In this post, I will explain how you can encrypt and decrypt data with Hibernate.
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