Programming the Perl DBI

DBI Architecture

The DBI architecture is split into two main groups of software: the DBI itself, and the drivers. The DBI defines the actual DBI programming interface, routes method calls to the appropriate drivers, and provides various support services to them. Specific drivers are implemented for each different type of database and actually perform the operations on the databases. Figure 4.1 illustrates this architecture.

Figure 4-1. The DBI architecture

Therefore, if you are authoring software using the DBI programming interface, the method you use is defined within the DBI module. From there, the DBI module works out which driver should handle the execution of the method and passes the method to the appropriate driver for actual execution. This is more obvious when you recognize that the DBI module does not perform any database work itself, nor does it even know about any types of databases whatsoever. Figure 4.2 shows the flow of data from a Perl script through to the database.

Figure 4-2. Data flow through DBI

Under this architecture, it is relatively straightforward to implement a driver for any type of database. All that is required is to implement the methods defined in the DBI specification,^[32] as supported by the DBI module, in a way that is meaningful for that database. The ...