The eval node

Evaluate one or more lambda expressions. For an explanation of lambdas, see lambda.

The list of lambda expressions given, will be evaluated top down. This means that a lambda can use the result of a previous expression.

The resulting fields named with the as parameter will be added to the current data-point.


|eval(lambda: "val" * 2, lambda: "double" / 2)
%% 'double' is also used in the second expression above
.as('double', 'val')

This example demonstrates the 'serial' behaviour of the eval node. The second expression uses the field double, which the first expression just created.

    lambda: int(str_concat(string(int("val")),string(int("val"))))

The string value of the field 'val' is concatenated to itself, this is then casted to an int value and added to the current data-point as the field ''.

For more lambda examples see lambda


Parameter Description Default
[node] lambdas( lambda_list ) list of lambda expressions
as( string_list ) list of output fieldnames (must have the same length as lambdas)
tags ( string_list ) list of output tagnames []