The collect_fields node

For every field in fields, holds the latest value and outputs a data-point item with these fields on every incoming data-point. If a field is not present in an input data-point, it will be ignored and the last known value for this field is used in output data.

It is possible to set a default value for fields that have not been seen so far.

With emit_unchanged set to false, no data is emitted for a data-point, that did not change any of the values.

If you need more complex collecting behaviors, take a look at the collect node.

Example

|json_emitter(
'{"hallo":"ho"}',
'{"ballo":"du", "sim": 3}',
'{"rallo":"su"}',
'{"gallo":"mu", "rallo": "srrt", "dim": 232.3}',
'{"mallo":"ffu"}',
'{"hallo":"hott"}',
'{"ballo":"dutt", "sim": 3}',
'{"rallo":"sutt", "rallo": "srrt", "dim": 232.3}',
'{"gallo":"mutt"}',
'{"mallo":"ffutt"}'
)
.select('rand')

|collect_fields('hallo', 'mallo', 'gallo')
.default(0.003)

This will output a data-point item with the fields hallo, mallo and gallo. Fields that have no value in the buffer yet, will get the default value.

Parameters

Parameter	Description	Default
[node]fields( string_list )	names of the fields used for each computation
default( any )	Default value for field, that have not been collected so far. If this is not given, that output item will only contain fields, that have been seen already.	undefined
keep(string_list)	If given, these fields will be included in output additionally to fields. The values for keep fields are taken from the current (incoming) data-point.	[]
keep_as(string_list)	Rename fields that are kept (must have the same number of entries as keep).	undefined
emit_unchanged (boolean)	When set to false, processing of a data-item that does not result in a change to the previous output, will not trigger an output of data. keep fields are excluded from this decision.	true