Should you delete records from your database or instead use a soft delete? I was recently asked my view on this question by a follower on Twitter. So what’s my answer? Well, I’m not usually thinking about “deleting” anything. Instead, I’m thinking about adding.
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So we’re all on the same page, let me take a step back and discuss deleting data in general. Hard deletes refer to removing the data from the database.
For example, with a table in a relational database, there are two records in the Employee table.
Doing a hard delete would mean executing a delete statement that would physically remove the record from the table. Only one record would be remaining.
Give yourself a high five if you got the movie reference to the remaining employee!
Typically if you’re using a relational database, you might have foreign key constraints that prevent you from deleting rows to enforce data integrity. You don’t want to have a reference to EmployeID123 in another table when it no longer exists.
Soft deletes solve this issue by often adding a column to indicate if the record/row is “deleted” or inactive.
For example, the table has an IsDeleted column deleted to False.
Instead of hard deleting, records are updated to have IsDeleted set to true.
Similarly, a property indicates if the document/object is deleted if you were working with a document database.
With a line of business and enterprise-style system, when working in the core part of a system, I’m often not thinking about deleting or soft deleting anything. This is because there are business concepts and business processes that don’t involve deleting data.
People within the domain don’t generally think about “deleting” data, nor would they use the term “delete” when talking about a business process or workflow.
Jumping back to my earlier example of employees, let’s say we were working within an HR system. An employee is a key aspect of the system, and there are different workflows around them. One of those concepts would be their employment history.
When an employee was terminated or quit, we wouldn’t just do a soft delete and mark them as “IsDeleted”. That doesn’t make sense. Employees would have a lifecycle of being hired and their employment terminated.
When an employee’s employment is terminated, other data is likely relevant to that event. When was it terminated, when was it effective, and what was its reason?
The key is that this is a business event that occurred, and we want to capture all the relevant data with that event.
Maybe we represent this in our document/object as a collection of hiring and terminations with the relevant data. It’s possible that an employee is re-hired at a later date and has multiple periods of employment.
Again the key is focusing on the business events that occur. If you think about events as a primary driver of your system, you’ll likely land into thinking about persisting events as a state. This is Event Sourcing. If you’re unfamiliar with the concept of Event Sourcing, check out my post Event Sourcing Example & Explained in plain English.
Now I can hear people screaming already; it’s just CRUD! While this can be true on the outer edge of a system that is more in a supporting role. In a large system, you’ll have various boundaries that act purely in supporting roles and are mostly reference data. And yes, this can be CRUD and would likely just soft delete.
However, at the core of your domain, as mentioned, you won’t hear people that understand the domain talk about “deleting.” Almost all events have some type of compensating action that ends the life cycle of a process or “undoes’s” or voids a previous action. Capturing those business events and concepts is key to building workflow within your system. If you’re focusing on CRUD, all business processes, workflows and understanding live entirely in the end-users head. Your system, at that point, is nothing more than a UI to a database with no real capabilities.
I can also hear people screaming, but… GDPR! I have to delete the data!
You’re missing the point.
If you need to delete data, delete it. The point isn’t about not deleting data; the point is that if you’re “soft deleting” data, you’re losing information about business concepts/events that have likely occurred as part of a business process or workflow. The events that occurred, and why they occurred can be incredibly valuable in building a robust system that can evolve as requirements change.
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