Configurable Functions

DataCaster supports configurable functions via the functions.xml config file in the db directory. This allows specifying static or non-static Java methods be invoked when SQL functions are used in SQL statements. These functions are available in all databases to all users. These are in addition to a few built-in functions that are in the core product.

This functions.xml conf file specifies the list of configured Functions, each of which needs a FunctionClass instance to implement the function. The supported attributes of Function are:

1. name: Function name used to specify the function.
2. FunctionClass: The class name of the Function class to be used, which must have a no-arg constructor if the method used is not static.

The FunctionProperty tags in the configuration of each function are as follows:

• MethodName: Required parameter for the method name to be used.
• ReturnType: Required parameter for the return type of the function.

For each function a set of zero or more Argument elements are specified. The Argument element has the following attributes

• name: The name of the argument, which is useful only to store the data in the system catalogs and hence must be unique across all Arguments in a method.
• type: The SQL data type of the argument.

Sample XML for a Function

The following is a sample of the XML for a function called MYMIN that call java.lang.Math.min as detailed below.

<Functions>
  <Function name="MYMIN" FunctionClass="java.lang.Math">
    <FunctionProperty name="MethodName" value="min" />
    <FunctionProperty name="ReturnType" value="INTEGER" />
    <Argument name="arg1" Type="INT">
        <ArgumentProperty name="Direction" value="IN" />
    </Argument>
    <Argument name="arg2" Type="INT">
    </Argument>
  </Function>
</Functions>