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Earlier today, I sparked a rather unexpected debate with my professional peers on the topic of foreign keys in our company's databases. In a nutshell, a software engineer who is senior to me stated that he didn't like a commit I had made to one of our repositories because I implemented a foreign-key relationship between two tables. His argument amounted to him not liking foreign keys because they restrict the data that can be inserted into the database & he believes that makes the database harder to work with. (Note: his argument was against foreign keys in general, not just the anecdotal foreign-key constraint that I proposed in our app. He believes that foreign-key constraints are a design flaw in modern relational database systems.)
At this point, I was caught completely flat-footed, and our boss chose to side with the senior developer for the time being, asking me to remove the foreign keys from my implementation of the bug-fix I was working on. The bug that I was fixing in fact stemmed from relational inconsistencies that were confusing our ORM (which itself leaves a bit to be desired, but that's a different story), and while I tried to explain this to my team, everyone sided with the senior dev & I was told to go back to the drawing board and re-implement my database fix WITHOUT relying upon foreign key constraints. In other words, I've been asked to do relational management without the built-in relational-management tools of our RDBMS (posgres, if it matters).
I reiterated that this was not the proper way to go about fixing the bug, at which point my boss told me that the discussion was taking up too much time and that if I wanted to debate the merits of formal FK-constraints, I would need to do it at a later date... which I intend to do, but I also feel like I've been tasked with arguing why water is wet.
When I go into this debate, I want to come armed with as many facts in support of foreign-key usage as possible. I know that implementing sensible FK-constraints:
- serves as an automatic guardrail against relational inconsistencies (ie, prevents "garbage data" (which is a demonstrable problem with the system I'm working on currently)),
- clarifies the high-level relational context between two related tables to someone who is inspecting the database schema, and
- can increase the performance of database query operations.
... But I'm wondering if there are any other bullet points that I may be missing on this topic with which I should meet this debate. What other benefits should I make sure to bring up with my boss and colleagues? (Or has there genuinely been a paradigm shift away from FK-constraints & I've been living with my head under a rock when it happened?)