Data Filtering: Logic vs Database Layer

Mohammed Osman // Programming


September 5  

Another insightful question from a junior developer:

“In a 3-Layer Architecture, should I filter specific objects in the data layer or the logic layer?”

Deciding where to filter your application data can be a challenging choice between two options: filtering at the database level (via SQL queries) or filtering at the code level (typically, the logic layer).

The direct answer is: Filter primarily at the database layer.

But Why?

Consider this analogy: You’re traveling from Paris to Dubai, and your friend Mustafa asks you to bring his favorite T-shirt from a suitcase he left in Paris.

You have two options:

  • Carry the entire suitcase from Paris to Dubai, then search for the T-shirt upon arrival. This is akin to filtering at the logic layer. You’re transferring a large database payload, which can severely impact your application’s performance.
  • Find the T-shirt in Paris and bring only that to Dubai. This corresponds to filtering at the database level. You’ll only transfer the data you need, making your application faster and more efficient.

Are There Exceptions?

Yes, there are scenarios where filtering at the logic layer may be more appropriate, but those are beyond the scope of this answer. The general rule of thumb is to prioritize filtering at the database layer.

In summary, stick to filtering at the database level.


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About the Author

Mohammed Osman