As with other entities, Flowman tries to automatically infer a meaningful documentation for mappings, especially for the schema of a relation. In order to do so, Flowman will query the original data source and look up any metadata (for example Flowman will pick up column descriptions in the Hive Metastore).
In order to provide additiona information, you can explicitly provide additional documentation for mappings via the
documentation tag, which is supported by all mappings.
relations: aggregates: kind: file format: parquet location: "$basedir/aggregates/" partitions: - name: year type: integer granularity: 1 # Explicit documentation section for annotating columns of the relation documentation: description: "The table contains all aggregated measurements" columns: # You can document any column you like, you don't have to provide a description for all of them - name: country description: "Country of the weather station" - name: min_temperature description: "Minimum air temperature per year in degrees Celsius" - name: max_temperature description: "Maximum air temperature per year in degrees Celsius" - name: avg_temperature description: "Average air temperature per year in degrees Celsius"
description(optional) (type: string): A description of the mapping
columns(optional) (type: schema): A documentation of the output schema. Note that Flowman will inspect the schema of the mapping itself and only overlay the provided documentation. Only fields found in the original output schema will be documented, so you cannot add fields to the documentation which actually do not exist.