protected final RelDataType getFloatType() {
        RelDataTypeFactory typeFactory = rexBuilder.getTypeFactory();
        RelDataType notNullFloatType = typeFactory.createSqlType(SqlTypeName.FLOAT);
        RelDataType floatType = typeFactory.createTypeWithNullability(notNullFloatType, true);
        return floatType;
      }
Generic support for rewriting Windowing expression into a different form usually using joins.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRewriteToDataSketchesRules.java