# OPAL Special Functions¶

Special functions implement flow control-like structures or other control semantics.

Function

Description

case

Return a matching result if the given condition is true.

group_by

Grouping/partitioning in which to process data.

m

Select a metric for the align verb.

metric

Select the metrics in the rollup verb.

options

Specify options to change the verb’s behavior

primary_key

Specify the primary key for some verbs

valid_for

Specify the validity period for each event for some verbs

window

Evaluates its argument in windowed context, partitioned over the given grouping and ordered by the given ordering (by default