scala sparkの勉強備忘録④ ~spark sqlでdataframeのarray listのカラムにあれこれ~

データ作り

scala> val t1 = Array(35, 36, 32, 30, 40, 42, 38)
t1: Array[Int] = Array(35, 36, 32, 30, 40, 42, 38)

scala> val t2 = Array(31, 32, 34, 55, 56)
t2: Array[Int] = Array(31, 32, 34, 55, 56)

scala> val tC = Seq(t1, t2).toDF("celsius")
tC: org.apache.spark.sql.DataFrame = [celsius: array<int>]

scala> tC.show()
+--------------------+
|             celsius|
+--------------------+
|[35, 36, 32, 30, ...|
|[31, 32, 34, 55, 56]|
+--------------------+

scala> tC.createOrReplaceTempView("tC")
# これでspark.sqlで色々弄れるっぽい
# ()内の文字列をspark.sqlでのfromで指定する形になる

transform（）

arraylistの全体の値を色々弄れる

scala> spark.sql("""
     | SELECT celsius, transform(celsius, t -> ((t*9) div 5) + 32) AS fahrenheit
     | FROM tC
     | """).show()
+--------------------+--------------------+
|             celsius|          fahrenheit|
+--------------------+--------------------+
|[35, 36, 32, 30, ...|[95, 96, 89, 86, ...|
|[31, 32, 34, 55, 56]|[87, 89, 93, 131,...|
+--------------------+--------------------+
# divは除算の小数点切り捨て

filter()

listのデータを条件付けで抽出する

scala> spark.sql("""
     | SELECT celsius, filter(celsius, t -> t>38) AS high
     | FROM tC
     | """).show()
+--------------------+--------+
|             celsius|    high|
+--------------------+--------+
|[35, 36, 32, 30, ...|[40, 42]|
|[31, 32, 34, 55, 56]|[55, 56]|
+--------------------+--------+

scala> spark.sql("""
     | SELECT celsius, filter(celsius, t -> t>38 and t<41) AS soso
     | FROM tC
     | """).show()
+--------------------+----+
|             celsius|soso|
+--------------------+----+
|[35, 36, 32, 30, ...|[40]|
|[31, 32, 34, 55, 56]|  []|
+--------------------+----+
#　複数の条件をつけるときはandとかor
# &だとダメだった

exists()

条件に合う値がlist内にあるかのtrue, false

scala> spark.sql("""
     | SELECT celsius, exists(celsius, t -> t=38) AS threshold
     | FROM tC
     | """).show()
+--------------------+---------+
|             celsius|threshold|
+--------------------+---------+
|[35, 36, 32, 30, ...|     true|
|[31, 32, 34, 55, 56]|    false|
+--------------------+---------+

scala> spark.sql("""
     | SELECT celsius, exists(celsius, t -> t>38 and t<41) AS threshold
     | FROM tC
     | """).show()
+--------------------+---------+
|             celsius|threshold|
+--------------------+---------+
|[35, 36, 32, 30, ...|     true|
|[31, 32, 34, 55, 56]|    false|
+--------------------+---------+
#こっちもandで複数行ける