Schema inheritance

In order to reduce amount of generated code, previously generated DataSchema interfaces are reused and only new properties are introduced

Let's filter out all null values from age column and add one more column of type Boolean:

val filtered = df.filter { age != null }.add("isAdult") { age!! > 18 }

New schema interface for filtered variable will be derived from previously generated DataFrameType:

@DataSchema
interface DataFrameType1 : DataFrameType

Extension properties for data access are generated only for new and overridden members of DataFrameType1 interface:

val ColumnsContainer<DataFrameType1>.age: DataColumn<Int> get() = this["age"] as DataColumn<Int>
val DataRow<DataFrameType1>.age: Int get() = this["age"] as Int
val ColumnsContainer<DataFrameType1>.isAdult: DataColumn<Boolean> get() = this["isAdult"] as DataColumn<Boolean>
val DataRow<DataFrameType1>.isAdult: String get() = this["isAdult"] as Boolean

Then variable filtered is cast to new interface:

val temp = filtered

val filtered = temp.cast<DataFrameType1>()

24 October 2025