| Optimization / Optimize your programs | |
The CHAR and VARCHAR data types are provided to hold string data from a database column. When you define a CHAR or VARCHAR variable with a length of 1000, the runtime system must allocate the entire size, to be able to fetch SQL data directly into the internal string buffer.
For character string data that is not stored in the database, consider using the STRING data type. The STRING type is similar to VARCHAR, except that you don't need to specify a maximum length and the internal string buffer is allocated dynamically as needed. Thus, by default, a STRING variable initially requires just a bunch of bytes, and grows during the program life time, with a limitation of 65534 bytes.
A STRING variable should typically be used to build SQL statements dynamically, for example from a CONSTRUCT instruction. You may also use the STRING type for utility function parameters, to hold file names for example.
After a large STRING variable is used, it should be cleared with a LET or a INITIALIZE TO NULL instruction. However, this is only needed for STRING variables declared as global or module variables. The variables defined in functions will be automatically destroyed when the program returns from the function.
The base.StringBuffer build-in class should be used for heavy string manipulation and modifications. String data is not copied on the stack when an object of this class is passed to a function, or when the string is modified with class methods. This can have a big impact on performance when very large strings are processed.