Prefilters

A prefilter allows you to define the initial filtering that should be applied to the datasource before returning any data.

The prefilter can either be provided as a configuration using the default mode or as an expression using the expression mode.

The mode can be controlled with the "filter" icon next to the expression.

Default mode

The default mode allows you to pass in the prefilter as a configuration.

prefilter default
Figure 1. The screenshot illustrates the prefilter user interface with the default mode enabled.

The first input defines what column should be involved with filtering.

The second input defines the comparator operator to use.

Different column types may define different comparator operators.

The third input defines the value that should be checked against the column using the specified comparator operator.

Expression mode

The expression mode allows you to pass in the prefilter as an expression, allowing you to cover more complex cases.

The screenshot illustrates the prefilter user interface with the expression mode enabled.

prefilter expression

Refer to the expression reference for details on writing expressions.

An example expression to return rows where the column Foo is greater or equal to 10: Foo >= 10

An example expression to return rows where the column Foo is equal to the string Foo = 'Bar'