High Performance MySQL [Electronic resources] نسخه متنی

Chapter 4. Indexes

Indexes
allow MySQL to quickly find and retrieve a set of records from the
millions or even billions that a table may contain. If
you've been using MySQL for any length of time,
you've probably created indexes in the hopes of
getting lighting-quick answers to your queries. And
you've probably been surprised to find that MySQL
didn't always use the index you thought it would.

For many users, indexes are something of a black art. Sometimes they
work wonders, and other times they seem just to slow down inserts and
get in the way. And then there are the times when they work fine for
a while, then begin to slowly degrade.

In this chapter, we'll begin by looking at some of
the concepts behind indexing and the various types of indexes MySQL
provides. From there, we'll cover some of the
specifics in MySQL's implementation of indexes. The
chapter concludes with recommendations for selecting columns to index
and the longer term care and feeding of your indexes.