The multi_map node

Maps fields from a json lookup table with data from the current data_item. This node can basically do what multiple select_first expression can do:

Example

def variables = '[{"mod_num":4233, "alarm_name": "E1_failed", "alarm_text": "Error", "type": "E1"}, ...]'

|multi_map()
.fields('module', 'alarm')                    
.match_fields('mod_num', 'alarm_name')        % Match these fields from the look-up table 
.select_fields('alarm_text', 'type')    
.lookup(variables)                                  

% is equivalent to:

|eval(
    lambda: select_first('alarm_text', [{'mod_num', "module"}, {'alarm_name', "alarm"}], variables),
    lambda: select_first('type', [{'mod_num', "module"}, {'alarm_name', "alarm"}], variables)
)
.as('alarm_text', 'type')

Here we match 'module_number' and 'alarm_name' in the lookup table against the values of the data_point fields 'module' and 'alarm'. From the resulting object we select two fields 'alarm_text', 'alarm_type' and add the to them data_point.

Parameters

Parameter	Description	Default
fields( string_list )	list of fieldnames from the current data_point to match data in the lookup table
match_fields( string_list )	list of fields in the lookup table to match the values of fields
select_fields( string_list )	select this fields from the lookup for output
lookup( string )	json object list in string format
as( string_list)	list of new field names for the selected fields, if given, must have the same count of names as select_fields	undefined