concat_ws从spark数据帧的输出中删除空字符串

Question

这是我的数据框的输出

val finaldf.show(false)

+------------------+-------------------------+---------------------+---------------+-------------------------+--------------+----------+----------+---------+-------------------------+-------------------------+-----------------------+---------------------------+--------------------------+-------------------+-----------------------+--------------------+------------------------+------------+----------------------+-----------+
|DataPartition     |TimeStamp                |Source_organizationId|Source_sourceId|FilingDateTime           |SourceTypeCode|DocumentId|Dcn       |DocFormat|StatementDate            |IsFilingDateTimeEstimated|ContainsPreliminaryData|CapitalChangeAdjustmentDate|CumulativeAdjustmentFactor|ContainsRestatement|FilingDateTimeUTCOffset|ThirdPartySourceCode|ThirdPartySourcePriority|SourceTypeId|ThirdPartySourceCodeId|FFAction|!||
+------------------+-------------------------+---------------------+---------------+-------------------------+--------------+----------+----------+---------+-------------------------+-------------------------+-----------------------+---------------------------+--------------------------+-------------------+-----------------------+--------------------+------------------------+------------+----------------------+-----------+
|SelfSourcedPrivate|2017-11-02T10:23:59+00:00|4298009288           |80             |2017-09-28T23:00:00+00:00|10K           |null      |171105584 |ASFILED  |2017-07-31T00:00:00+00:00|false                    |false                  |2017-07-31T00:00:00+00:00  |1.0                       |false              |-300                   |SS                  |1                       |3011835     |1000716240            |I|!|       |
|SelfSourcedPublic |2017-11-21T12:09:23+00:00|4295904170           |364            |2017-08-08T17:00:00+00:00|10Q           |null      |null      |null     |2017-07-30T00:00:00+00:00|false                    |false                  |2017-07-30T00:00:00+00:00  |1.0                       |false              |-300                   |SS                  |1                       |3011836     |1000716240            |I|!|       |
|SelfSourcedPublic |2017-11-21T12:09:23+00:00|4295904170           |365            |2017-10-10T17:00:00+00:00|10K           |null      |null      |null     |2017-09-30T00:00:00+00:00|false                    |false                  |2017-09-30T00:00:00+00:00  |1.0                       |false              |-300                   |SS                  |1                       |3011835     |1000716240            |I|!|       |
|SelfSourcedPublic |2017-11-21T12:17:49+00:00|4295904170           |365            |2017-10-10T17:00:00+00:00|10K           |null      |null      |null     |2017-09-30T00:00:00+00:00|false                    |false                  |2017-09-30T00:00:00+00:00  |1.0                       |false              |-300                   |SS                  |1                       |3011835     |1000716240            |I|!|       |

什么时候concat_ws null从行中删除。

val finaldf = diff.foldLeft(tempReorder){(temp2df, colName) => temp2df.withColumn(colName, lit("null"))}
//finaldf.show(false)

val headerColumn = data.columns.toSeq
val header = headerColumn.mkString("", "|^|", "|!|").dropRight(3)

val finaldfWithDelimiter=finaldf.select(concat_ws("|^|",finaldf.schema.fieldNames.map(col): _*).as("concatenated")).withColumnRenamed("concatenated", header)
finaldfWithDelimiter.show(false)

我得到低于输出

+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|DataPartition|^|TimeStamp|^|Source_organizationId|^|Source_sourceId|^|FilingDateTime|^|SourceTypeCode|^|DocumentId|^|Dcn|^|DocFormat|^|StatementDate|^|IsFilingDateTimeEstimated|^|ContainsPreliminaryData|^|CapitalChangeAdjustmentDate|^|CumulativeAdjustmentFactor|^|ContainsRestatement|^|FilingDateTimeUTCOffset|^|ThirdPartySourceCode|^|ThirdPartySourcePriority|^|SourceTypeId|^|ThirdPartySourceCodeId|^|FFAction|!||
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|SelfSourcedPrivate|^|2017-11-02T10:23:59+00:00|^|4298009288|^|80|^|2017-09-28T23:00:00+00:00|^|10K|^|171105584|^|ASFILED|^|2017-07-31T00:00:00+00:00|^|false|^|false|^|2017-07-31T00:00:00+00:00|^|1.0|^|false|^|-300|^|SS|^|1|^|3011835|^|1000716240|^|I|!|                                                                                                                                                                 |
|SelfSourcedPublic|^|2017-11-21T12:09:23+00:00|^|4295904170|^|364|^|2017-08-08T17:00:00+00:00|^|10Q|^|2017-07-30T00:00:00+00:00|^|false|^|false|^|2017-07-30T00:00:00+00:00|^|1.0|^|false|^|-300|^|SS|^|1|^|3011836|^|1000716240|^|I|!|                                                                                                                                                                                       |
|SelfSourcedPublic|^|2017-11-21T12:09:23+00:00|^|4295904170|^|365|^|2017-10-10T17:00:00+00:00|^|10K|^|2017-09-30T00:00:00+00:00|^|false|^|false|^|2017-09-30T00:00:00+00:00|^|1.0|^|false|^|-300|^|SS|^|1|^|3011835|^|1000716240|^|I|!|   

在输出中DocumentId，将替换为null。

无法找出我想念的是什么？

Answer 1

concat_ws确实null在连接过程中删除了列。如果要为null串联结果中的每个保留一个占位符，则一种方法是创建一个Map类型依赖的colName -> nullValue，na.fill()以便在串联之前转换数据帧，如下所示：

val df = Seq(
  (new Integer(1), "a"),
  (new Integer(2), null),
  (null, "c")
).toDF("col1", "col2")

df.withColumn("concat", concat_ws("|", df.columns.map(col): _*)).
  show
// +----+----+------+
// |col1|col2|concat|
// +----+----+------+
// |   1|   a|   1|a|
// |   2|null|     2|
// |null|   c|     c|
// +----+----+------+

val naMap = df.dtypes.map( t => t._2 match {
  case "StringType" => (t._1, "(n/a)")
  case "IntegerType" => (t._1, 0)
  case "LongType" => (t._1, 0L)
  // cases for other types ...
} ).toMap
// naMap: scala.collection.immutable.Map[String,Any] = 
//   Map(col1 -> 0, col2 -> (n/a))

df.na.fill(naMap).
  withColumn("concat", concat_ws("|", df.columns.map(col): _*)).
  show
// +----+-----+-------+
// |col1| col2| concat|
// +----+-----+-------+
// |   1|    a|    1|a|
// |   2|(n/a)|2|(n/a)|
// |   0|    c|    0|c|
// +----+-----+-------+