Hitachi Vantara Pentaho Community Wiki

08. Functions and Expressions

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Functions have access to the data row and can access other functions or expressions or the data source. Functions are stateful meaning they maintain their state during the report generation. For stateless user-defined computations, consider using an expression instead of functions, as expression are cheaper to compute and maintain when using huge reports. Function parameters are given by property elements.

The deplevel attribute can be used to prioritize the functions. Functions with an higher dependency level are executed before any function with lower dependency levels. Dependency levels lower than 0 are not allowed.

An expression is a stateless user-defined function. It can access the data row and the report properties (property-ref) to perform its task. Using the data row, an expression has access to the data source and other functions and expressions. Expression parameters are given by property elements.

Function/Expression Type Description
Summary Calculations These calculate values for display in groups, headers and footers.
Item Calculations These calculate values for display in item (detail) bands.
Advanced Calculations These are misc. advanced calculations.
Pentaho Charting Extensions These are functions and expressions for generating charts within reports.
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