MySQL - why not index every field?

Question

Recently I\'ve learned the wonder of indexes, and performance has improved dramatically. However, with all I\'ve learned, I can\'t seem to find the answer to this question.<

Answer 1

Indexing will take up more allocated space both from drive and ram, but also improving the performance a lot. Unfortunately when it reaches memory limit, the system will surrender the drive space and risk the performance. Practically, you shouldn't index any field that you might think doesn't involve in any kind of data traversing algorithm, neither inserting nor searching (WHERE clause). But you should if otherwise. By default you have to index all fields. The fields which you should consider unindexing is if the queries are used only by moderator, unless if they need for speed too