Oracle Web Applications: PL/SQL Developer's Intro

Text Processing

The enormous popularity of Perl is due in large part to its sophisticated text processing capabilities. A single Perl command can replace dozens of PL/SQL INSTR and SUBSTR operations. Additionally, Perl’s pattern matching capabilities are well suited for processing and validating the text entered into HTML forms.

The PL/SQL toolkit has two packages that bring a subset of these capabilities to PL/SQL. The first, OWA_TEXT, manipulates large chunks of text. The second, OWA_PATTERN, allows developers to use sophisticated search patterns to perform many of the text operations found in Perl.

Beyond their mere utility, these two packages are interesting examples of good package design. OWA_TEXT is similar to the abstract datatypes described in Chapter 6. OWA_PATTERN builds on OWA_TEXT to create dozens of variations of the search and replace procedure, each useful in particular circumstances.

OWA_TEXT: Representing Text

The largest PL/SQL string can contain 32,767 characters. Unfortunately, there are many cases where we might like to process larger chunks of text. A document indexing system, for example, must almost certainly process files much larger than 32K.^[15] The OWA_TEXT package overcomes the 32K limitation by breaking text streams into smaller pieces that are stored as elements in a PL/SQL array.

Additionally, it is often useful to treat the components of a string as a single entity (e.g., a sentence as an array of words). OWA_TEXT is ideal for this type of application. ...