kishoreg opened a new pull request #4388: Adding support for Map type fields URL: https://github.com/apache/incubator-pinot/pull/4388 This leverages existing features MultiValue feature in Pinot. A Map is represented as two Multi-valued columns - __KEYS and __VALUES. This convention is used in only one place - real-time ingestion and segment generation. When pinot sees a FieldSpec name that ends with __KEYS or __VALUES, it checks for the field in the input Record. If that object turns out to be a map, then we convert it into two columns -> keyArray and valueArray. Once we ingest a map as two arrays, we can access map['keyName'] via udf map_value(keyColumnName, 'KeyName', valueColumnName). We can support the simpler syntax when we move to calcite. Sample queries ```select map_value(myMap__KEYS, 'k1', myMap__VALUES) from myTable``` ```select count(*) from myTable group by map_value(myMap__KEYS, 'k1', myMap__VALUES)``` ```select count(*) from myTable where map_value(myMap__KEYS, 'k1', myMap__VALUES) = 'v1'``` NOTE: While this solution is not elegant, it is a good first step towards supporting Map and Struct data types. Supporting Map as a DataType was bit invasive and requires us to first introduce the concept of CompositeColumnDatasource.
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