Grammar

gather Operation Grammar

(What is this notation?)

gather{ columnsSelector: ColumnsSelector}

    [ .explodeLists() ]

    [ .cast<T>() ]

    [ .notNull() ]

    [ .where{ filter: RowValueFilter} ]

    [ .mapKeys{ transform: (String) -> K } ]

    [ .mapValues{ transform: (C) -> R} ]

    .into(keyColumn: String, valueColumn: String)

    | .keysInto(keyColumn: String)

    | .valuesInto(valueColumn: String)