Expression Mapping¶

This feature allows to add a derivated column or modify the current column value in your mapping that evaluates a expression or get the value of a variable for a new mapping column.

mapping.string.0.Value

It's possible to evaluate the value of a mapping and create a derivated column with expression with the key source_is_expression in true and format the expression in this form in the column source:

mapping.string.0 + ' ' + mapping.string.1

This means that the column is a expression where mapping index 0 will be concatenated with mapping index 1. Example mapping:

[[jobs.mapping]]
column_source = 'firstname'
column_destination = 'firstname'

[[jobs.mapping]]
column_source = 'lastname'
column_destination = 'lastname'

[[jobs.mapping]]
column_source = 'mapping.string.0 + ' ' + mapping.string.1'
source_is_expression = true
column_destination = 'concatenated_name'

The expression mapping can be a normal expression without a mapping index column, but in v1.7.0 and below, the expression mapping should have always a mapping column index. If there isn't a mapping index it will through an error.

The string in the expression mapping it's the expected type of value. If value is a integer for example, it will be converted, but if you specified int and the value returned in the mapping is a string and cannot be converted to int, then an error is triggered.

If you change the order, the index also changes. This example add concatenated_name to beginning:

[[jobs.mapping]]
column_source = 'mapping.string.1 + ' ' + mapping.string.2'
source_is_expression = true
column_destination = 'concatenated_name'

[[jobs.mapping]]
column_source = 'firstname'
column_destination = 'firstname'

[[jobs.mapping]]
column_source = 'lastname'
column_destination = 'lastname'

Also you can omit the columns for only get the derivated column:

[[jobs.mapping]]
column_source = 'mapping.string.1 + " " + mapping.string.2'
source_is_expression = true
column_destination = 'concatenated_name'

[[jobs.mapping]]
column_source = 'firstname'
column_destination = 'firstname'
omit = true

[[jobs.mapping]]
column_source = 'lastname'
column_destination = 'lastname'
omit = true

Apply expression to same column¶

You can modify the same column using this instead index and the key apply_expression with the expression instead source_is_expression:

[[jobs.mapping]]
column_source = 'firstname'
column_destination = 'firstname'
omit = true

[[jobs.mapping]]
column_source = 'lastname'
apply_expression = 'mapping.string.0 + " " + mapping.string.this'
column_destination = 'fullname'

With variables¶

Also is possible to add a variable value, simply add a mapping where column source key source_is_variable is true and column_source is the name of a variable. Example:

[[jobs.mapping]]
column_source = 'my_variable'
source_is_variable = true
column_destination = 'lastname'

The variable can be any type, it will converted. Also the variable can have a expression.