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CGI Programming with Perl, 2nd Edition by Gunther Birznieks, Shishir Gundavaram, Scott Guelich

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Chapter 10. Data Persistence

Many basic web applications can be created that output only email and web documents. However, if you begin building larger web applications, you will eventually need to store data and retrieve it later. This chapter will discuss various ways to do this with different levels of complexity. Text files are the simplest way to maintain data, but they quickly become inefficient when the data becomes complex or grows too large. A DBM file provides much faster access, even for large amounts of data, and DBM files are very easy to use with Perl. However, this solution is also limited when the data grows too complex. Finally, we will investigate relational databases. A relational database management system (RDBMS) provides high performance even with complex queries. However, an RDBMS is more complicated to set up and use than the other solutions.

Applications evolve and grow larger. What may start out as a short, simple CGI script may gain feature upon feature until it has grown to a large, complex application. Thus, when you design web applications, it is a good idea to develop them so that they are easily expandable.

One solution is to make your solutions modular. You should try to abstract the code that reads and writes data so the rest of the code does not know how the data is stored. By reducing the dependency on the data format to a small chunk of code, it becomes easier to change your data format as you need to grow.

Text Files

One of Perl’s greatest strengths ...

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