Schema inheritance

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

API reference: DataSchema

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>()

02 November 2026