TIL, 2017-04-26, Database Indexing

Inheriting Code: Why You Should Keep Code Teardowns to Yourself

When passing a project to new owners, initial reactions are almost always too harsh. It’s very easy to be a critic, especially of someone else’s.
Assume best intent and try to look at things optimistically.
It is overwhelmingly likely that the team or person who wrote the code did so in a different context than the one you’re in today.
We should not lose sight of leaving things in a better state than when we found them.
Don’t be intimidated by a code base that you’re unfamiliar with–my recommendation is to dig in, focus on how you can test or verify what you’re doing, and start making small changes.

An index is a data structure that stores the values for a specific column in a table. It is created on a column of a table. An index on User#name will search for John faster because all names starting with a “J” will be right next to each other in the index.
On average, searching a field without index will take N/2. With a sorted field, it is log 2 N. Also, since the data is sorted given a non-key field, the rest of the table doesn’t need to be searched for duplicate values once a higher value is found.
Downside: these require additional space on the disk.