Project mistakes

src/teaching/cse-562/2017sp/project-mistakes.md

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+---
+title: CSE-562; Common Project Mistakes
+---
+### Use Strings instead of Enums in inner loops
+
+`myString.equals("test")` is slooooooow.  If the number of times that you need to call this function scales with the number of tuples in the data, consider using an [Enum type](http://docs.oracle.com/javase/tutorial/java/javaOO/enum.html) instead.  
+
+### Non-compositional code
+
+Maintaining separation of concerns is important.  You *can* create one big main function that evaluates the entire query, but by checkpoint 2 it's going to become a mess of spaghetti code and a nightmare to maintain and debug.  Break it up into smaller components.  As mentioned in class, if you could have all of the logic encapsulated in a function, that would be the best possible option.  However, since that requires `O(N)` memory, instead you should encapsulate the logical elements in iterators: Create a "Filtering" iterator, a "Mapping" iterator, an "Aggregating" iterator, etc...