Why the input type Spark UDF is Row for struct column? How is it implemented in Spark?
0
For single column, the input type of UDF is the dataType of this column, while for struct column, the input type is Row, why and how is it implemented?
import org.apache.spark.sql.types._
import org.apache.spark.sql.Row
val sub_schema = StructType(StructField("col1",ArrayType(IntegerType,false),true) :: StructField("col2",StringType,true)::Nil)
val schema = StructType(StructField("subtable", sub_schema,true) :: Nil)
val data = Seq(Row(Row(Array(1,2),"eb")), Row(Row(Array(3,2,1), "dsf")) )
val rd = sc.parallelize(data)
val df = spark.createDataFrame(rd, schema)
df.printSchema
val u = udf((x:Row) => x, sub_schema)
root
|-- subtable: struct (nullable = true)
| |-- col1: array (nullable = true)
| | |-- element: integer (containsNull = false)
| |-- col2: string (nullable = true)
Spark UDF for StructType / Row
apache-spark
asked Nov 14 '18 at 12:17
KamelKamel
9801822
add a comment |
0
For single column, the input type of UDF is the dataType of this column, while for struct column, the input type is Row, why and how is it implemented?
import org.apache.spark.sql.types._
import org.apache.spark.sql.Row
val sub_schema = StructType(StructField("col1",ArrayType(IntegerType,false),true) :: StructField("col2",StringType,true)::Nil)
val schema = StructType(StructField("subtable", sub_schema,true) :: Nil)
val data = Seq(Row(Row(Array(1,2),"eb")), Row(Row(Array(3,2,1), "dsf")) )
val rd = sc.parallelize(data)
val df = spark.createDataFrame(rd, schema)
df.printSchema
val u = udf((x:Row) => x, sub_schema)
root
|-- subtable: struct (nullable = true)
| |-- col1: array (nullable = true)
| | |-- element: integer (containsNull = false)
| |-- col2: string (nullable = true)
Spark UDF for StructType / Row
apache-spark
asked Nov 14 '18 at 12:17
KamelKamel
9801822
Could explain why do you find it unusual? What else would you expect?
– user10465355
Nov 14 '18 at 13:14
Because the input type of UDF is by convention, which is implemented using reflection and can not be inferred by static type checking.
– Kamel
Nov 15 '18 at 1:47
add a comment |
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For single column, the input type of UDF is the dataType of this column, while for struct column, the input type is Row, why and how is it implemented?
import org.apache.spark.sql.types._
import org.apache.spark.sql.Row
val sub_schema = StructType(StructField("col1",ArrayType(IntegerType,false),true) :: StructField("col2",StringType,true)::Nil)
val schema = StructType(StructField("subtable", sub_schema,true) :: Nil)
val data = Seq(Row(Row(Array(1,2),"eb")), Row(Row(Array(3,2,1), "dsf")) )
val rd = sc.parallelize(data)
val df = spark.createDataFrame(rd, schema)
df.printSchema
val u = udf((x:Row) => x, sub_schema)
root
|-- subtable: struct (nullable = true)
| |-- col1: array (nullable = true)
| | |-- element: integer (containsNull = false)
| |-- col2: string (nullable = true)
Spark UDF for StructType / Row
apache-spark
asked Nov 14 '18 at 12:17
KamelKamel
9801822
For single column, the input type of UDF is the dataType of this column, while for struct column, the input type is Row, why and how is it implemented?
import org.apache.spark.sql.types._
import org.apache.spark.sql.Row
val sub_schema = StructType(StructField("col1",ArrayType(IntegerType,false),true) :: StructField("col2",StringType,true)::Nil)
val schema = StructType(StructField("subtable", sub_schema,true) :: Nil)
val data = Seq(Row(Row(Array(1,2),"eb")), Row(Row(Array(3,2,1), "dsf")) )
val rd = sc.parallelize(data)
val df = spark.createDataFrame(rd, schema)
df.printSchema
val u = udf((x:Row) => x, sub_schema)
root
|-- subtable: struct (nullable = true)
| |-- col1: array (nullable = true)
| | |-- element: integer (containsNull = false)
| |-- col2: string (nullable = true)
Spark UDF for StructType / Row
apache-spark
apache-spark
asked Nov 14 '18 at 12:17
KamelKamel
9801822
asked Nov 14 '18 at 12:17
KamelKamel
9801822
asked Nov 14 '18 at 12:17
KamelKamel
9801822
asked Nov 14 '18 at 12:17
KamelKamel
9801822
asked Nov 14 '18 at 12:17
KamelKamel
9801822
9801822
Could explain why do you find it unusual? What else would you expect?
– user10465355
Nov 14 '18 at 13:14
Because the input type of UDF is by convention, which is implemented using reflection and can not be inferred by static type checking.
– Kamel
Nov 15 '18 at 1:47
add a comment |
Could explain why do you find it unusual? What else would you expect?
– user10465355
Nov 14 '18 at 13:14
Because the input type of UDF is by convention, which is implemented using reflection and can not be inferred by static type checking.
– Kamel
Nov 15 '18 at 1:47
Could explain why do you find it unusual? What else would you expect?
– user10465355
Nov 14 '18 at 13:14
Could explain why do you find it unusual? What else would you expect?
– user10465355
Nov 14 '18 at 13:14
Because the input type of UDF is by convention, which is implemented using reflection and can not be inferred by static type checking.
– Kamel
Nov 15 '18 at 1:47
Because the input type of UDF is by convention, which is implemented using reflection and can not be inferred by static type checking.
– Kamel
Nov 15 '18 at 1:47
add a comment |
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Could explain why do you find it unusual? What else would you expect?
– user10465355
Nov 14 '18 at 13:14
Because the input type of UDF is by convention, which is implemented using reflection and can not be inferred by static type checking.
– Kamel
Nov 15 '18 at 1:47