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www.it-ebooks.infoCHAPTER 25 • INTRODUCING MYSQL5.0 is proof of this commitment, with all of the aforementioned features now available (subqueries wereintroduced in version 4.1). Several subsequent chapters of this book are devoted to these relatively newfeatures.Full-Text Indexing and SearchingMySQL has long supported full-text indexing and searching, a feature that greatly enhances theperformance of mining data from text-based columns. This feature also enables you to produce resultsin order of relevance in accordance with how closely the query matches the row’s indexed textualcolumns. This feature is covered in Chapter 36.Query CachingQuery caching is one of MySQL’s greatest speed enhancements. Simple and highly effective whenenabled, query caching allows MySQL to store SELECT queries, along with their corresponding results,in memory. As subsequent queries are executed, MySQL compares them against the cached queries; ifthey match, MySQL forgoes the costly database retrieval and instead dumps the cached query result. Toeliminate outdated results, mechanisms are built in to automatically remove invalidated cache resultsand re-cache them upon the next request.ReplicationReplication allows a database located within one MySQL server to be duplicated on another, whichprovides a great number of advantages. For instance, just having a single slave database in place cangreatly increase availability, because it can be brought online immediately if the master databaseexperiences a problem. If you have multiple machines at your disposal, client queries can be spreadacross the master and multiple slaves, considerably reducing the load that would otherwise be incurredon a single machine. Another advantage involves backups; rather than take your application offlinewhile a backup completes, you can instead execute the backup on a slave, avoiding any downtime.SecurityMySQL sports a vast array of security and configuration options, enabling you to wield total control overjust about every imaginable aspect of its operation. For example, with MySQL’s configuration optionsyou can control features such as the following:• The daemon owner, default language, default port, location of MySQL’s data store,and other key characteristics.• The amount of memory allocated to threads, the query cache, temporary tables,table joins, and index key buffers.• Various aspects of MySQL’s networking capabilities, including how long it willattempt to perform a connection before aborting, whether it will attempt toresolve DNS names, the maximum allowable packet size, and more.MySQL’s security options are equally impressive, allowing you to manage characteristics such as thefollowing:479