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[英]Is there a way to join two spark dataframes with custom join for each row
[英]What is the right way to join these 2 Spark DataFrames?
假設我有2個Spark DataFrame:
val addStuffDf = Seq(
("A", "2018-03-22", 5),
("A", "2018-03-24", 1),
("B", "2018-03-24, 3))
.toDF("user", "dt", "count")
val removedStuffDf = Seq(
("C", "2018-03-25", 10),
("A", "2018-03-24", 5),
("B", "2018-03-25", 1)
).toDF("user", "dt", "count")
最后,我想獲得一個具有摘要統計信息的單個數據框(實際上排序並不重要):
+----+----------+-----+-------+
|user| dt|added|removed|
+----+----------+-----+-------+
| A|2018-03-22| 5| 0|
| A|2018-03-24| 1| 5|
| B|2018-03-24| 3| 0|
| B|2018-03-25| 0| 1|
| C|2018-03-25| 0| 10|
+----+----------+-----+-------+
很明顯,我可以在“步驟0”處簡單地重命名“計數”列,以便具有數據幀df1
和df2
val df1 = addedDf.withColumnRenamed("count", "added")
df1.show()
+----+----------+-----+
|user| dt|added|
+----+----------+-----+
| A|2018-03-22| 5|
| A|2018-03-24| 1|
| B|2018-03-24| 3|
+----+----------+-----+
val df2 = removedDf.withColumnRenamed("count", "removed")
df2.show()
+----+----------+-------+
|user| dt|applied|
+----+----------+-------+
| C|2018-03-25| 10|
| A|2018-03-24| 5|
| B|2018-03-25| 1|
+----+----------+-------+
但是現在我無法定義“步驟1”-即,確定將df1和df2壓縮在一起的轉換。 從邏輯的觀點來看, full_outer
連接將我需要的所有行都放在一個DF中,但是隨后我需要以某種方式合並重復的列:
df1.as('d1)
.join(df2.as('d2),
($"d1.user"===$"d2.user" && $"d1.dt"===$"d2.dt"),
"full_outer")
.show()
+----+----------+-----+----+----------+-------+
|user| dt|added|user| dt|applied|
+----+----------+-----+----+----------+-------+
|null| null| null| C|2018-03-25| 10|
|null| null| null| B|2018-03-25| 1|
| B|2018-03-24| 3|null| null| null|
| A|2018-03-22| 5|null| null| null|
| A|2018-03-24| 1| A|2018-03-24| 5|
+----+----------+-----+----+----------+-------+
如何將這些user
和dt
列合並在一起? 而且,總體而言-我是否使用正確的方法來解決我的問題,或者是否有更直接/有效的解決方案?
由於要為兩個DataFrame聯接的列具有匹配的名稱,因此對聯接條件使用Seq("user", "dt")
將產生您想要的合並表:
val addStuffDf = Seq(
("A", "2018-03-22", 5),
("A", "2018-03-24", 1),
("B", "2018-03-24", 3)
).toDF("user", "dt", "count")
val removedStuffDf = Seq(
("C", "2018-03-25", 10),
("A", "2018-03-24", 5),
("B", "2018-03-25", 1)
).toDF("user", "dt", "count")
val df1 = addStuffDf.withColumnRenamed("count", "added")
val df2 = removedStuffDf.withColumnRenamed("count", "removed")
df1.as('d1).join(df2.as('d2), Seq("user", "dt"), "full_outer").
na.fill(0).
show
// +----+----------+-----+-------+
// |user| dt|added|removed|
// +----+----------+-----+-------+
// | C|2018-03-25| 0| 10|
// | B|2018-03-25| 0| 1|
// | B|2018-03-24| 3| 0|
// | A|2018-03-22| 5| 0|
// | A|2018-03-24| 1| 5|
// +----+----------+-----+-------+
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