Multi Mapping
Description
The Multi Mapping transform re-uses a child pipeline (a mapping) with zero or more inputs and outputs.
Unlike Simple Mapping, which always has one Mapping input and one Mapping output, Multi Mapping can:
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start a child that generates its own data (0 inputs)
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run a child that only writes data (0 outputs)
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join or look up using several Mapping Input transforms
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split rows to several Mapping Output transforms
Non-main input mappings become info hops (the same idea as Stream Lookup). Non-main output mappings become target hops (the same idea as Switch / Case).
That lets you wrap a reusable Stream Lookup or Switch / Case style pipeline.
The child pipeline is always executed with a local Hop pipeline run configuration so rows can be streamed in and out of the mapping.
Options
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Transform name: a unique name in your pipeline
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Pipeline: the mapping (sub-) pipeline to run
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Run configuration: local Hop run configuration only
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Parameters tab: variables to pass into the child, plus inherit-all-variables
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Input tabs (Add Input): one tab per input mapping
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Input source transform: parent transform that sends rows (empty = auto-detect remaining hops)
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Mapping Input transform: child Mapping Input that receives those rows
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Main data path: checked for the primary stream; unchecked for an info hop
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Update mapped field names downstream: reverse input renames on the way out
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Field mapping table
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Output tabs (Add Output): one tab per output mapping
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Mapping Output transform: child Mapping Output that produces rows
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Output target transform: parent transform that receives those rows (empty = auto-detect remaining hops)
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Main data path: checked for the primary stream; unchecked for a target hop
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Field mapping table
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You can close every input or output tab. A mapping with no inputs is a generator. A mapping with no outputs is a sink.
Sample
The samples project contains parent/child examples under transforms/ for a single stream, a generator, a join, an info lookup, and multiple target outputs.
For the exact rules that decide which value a parameter ends up with, see Passing parameters to a child pipeline or workflow.