“Flat is better than nested” - for data as well as code?

Question

This question got me thinking: should we apply the principle that \"flat is better than nested\" to data as well as to code? Even when there is a \"logical tree structure\" to t

Answer 1

This is a completely subjective question. The answer is, "it depends."

It depends on the primary use of your data. If you continually have to reference the nested structure, then it makes sense to represent it that way. And if you never reference the flat representation except when building the nested structure, then why have the flat structure at all?

The "flat" representation is one of the basics of the relational database model: each type of data exists in a table just for that type, and any relationships among the items are contained in separate tables. It's a useful abstraction, but at times difficult to work with in code. On the other hand, processing all the data of a particular type is trivial.

Consider, for example, if I wanted to find all the descendants of the record with id 2 in your example data. If the data is already in the hierarchy (i.e. native representation is the "nested" structure), then it's trivial to locate record id 2 and then traverse its children, children's children, etc.

But if the native representation is sequential as you've shown it then I have to pass through the entire data set to create the hierarchical structure and then find record 2 and its children.

So, as I said, "it depends."