Spark无法评估表达式：窗口表达式的滞后

Question

我正在尝试对Cassandra表中的数据框执行大量操作，然后将其保存在另一个表中。这些操作之一如下：

val leadWindow = Window.partitionBy(col("id")).orderBy(col("timestamp").asc).rowsBetween(Window.currentRow, 2)
df.withColumn("lead1", lag(sum(col("temp1")).over(leadWindow), 2, 0))

我在工作时遇到一个异常，说明无法评估lag操作。

2018-10-08 12:02:22 INFO  Cluster:1543 - New Cassandra host /127.0.0.1:9042 added
    2018-10-08 12:02:22 INFO  CassandraConnector:35 - Connected to Cassandra cluster: Test Cluster
    2018-10-08 12:02:23 INFO  CassandraSourceRelation:35 - Input Predicates: [IsNotNull(ts)]
    2018-10-08 12:02:23 INFO  CassandraSourceRelation:35 - Input Predicates: [IsNotNull(ts)]
    Exception in thread "main" java.lang.UnsupportedOperationException: Cannot evaluate expression: lag(input[43, bigint, true], 2, 0)
            at org.apache.spark.sql.catalyst.expressions.Unevaluable$class.doGenCode(Expression.scala:258)
            at org.apache.spark.sql.catalyst.expressions.OffsetWindowFunction.doGenCode(windowExpressions.scala:326)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:107)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:104)
            at scala.Option.getOrElse(Option.scala:121)
            at org.apache.spark.sql.catalyst.expressions.Expression.genCode(Expression.scala:104)
            at org.apache.spark.sql.catalyst.expressions.BinaryExpression.nullSafeCodeGen(Expression.scala:496)
            at org.apache.spark.sql.catalyst.expressions.BinaryExpression.defineCodeGen(Expression.scala:479)
            at org.apache.spark.sql.catalyst.expressions.Add.doGenCode(arithmetic.scala:174)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:107)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:104)
            at scala.Option.getOrElse(Option.scala:121)
            at org.apache.spark.sql.catalyst.expressions.Expression.genCode(Expression.scala:104)
            at org.apache.spark.sql.catalyst.expressions.BinaryExpression.nullSafeCodeGen(Expression.scala:496)
            at org.apache.spark.sql.catalyst.expressions.BinaryExpression.defineCodeGen(Expression.scala:479)
            at org.apache.spark.sql.catalyst.expressions.BinaryComparison.doGenCode(predicates.scala:513)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:107)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:104)
            at scala.Option.getOrElse(Option.scala:121)
            at org.apache.spark.sql.catalyst.expressions.Expression.genCode(Expression.scala:104)
            at org.apache.spark.sql.catalyst.expressions.And.doGenCode(predicates.scala:397)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:107)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:104)
            at scala.Option.getOrElse(Option.scala:121)
            at org.apache.spark.sql.catalyst.expressions.Expression.genCode(Expression.scala:104)
            at org.apache.spark.sql.catalyst.expressions.CaseWhen$$anonfun$8.apply(conditionalExpressions.scala:202)
            at org.apache.spark.sql.catalyst.expressions.CaseWhen$$anonfun$8.apply(conditionalExpressions.scala:201)
            at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
            at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
            at scala.collection.immutable.List.foreach(List.scala:381)
            at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
            at scala.collection.immutable.List.map(List.scala:285)
            at org.apache.spark.sql.catalyst.expressions.CaseWhen.doGenCode(conditionalExpressions.scala:201)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:107)
            at org.apache.spark.sql.catalyst.expressions.Expression$$anonfun$genCode$2.apply(Expression.scala:104)
            at scala.Option.getOrElse(Option.scala:121)
            at org.apache.spark.sql.catalyst.expressions.Expression.genCode(Expression.scala:104)
            at org.apache.spark.sql.catalyst.expressions.Alias.genCode(namedExpressions.scala:142)
            at org.apache.spark.sql.execution.ProjectExec$$anonfun$6.apply(basicPhysicalOperators.scala:60)
            at org.apache.spark.sql.execution.ProjectExec$$anonfun$6.apply(basicPhysicalOperators.scala:60)
            at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
            at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
            at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
            at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
            at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
            at scala.collection.AbstractTraversable.map(Traversable.scala:104)
            at org.apache.spark.sql.execution.ProjectExec.doConsume(basicPhysicalOperators.scala:60)
            at org.apache.spark.sql.execution.CodegenSupport$class.consume(WholeStageCodegenExec.scala:181)
            at org.apache.spark.sql.execution.InputAdapter.consume(WholeStageCodegenExec.scala:354)
            at org.apache.spark.sql.execution.InputAdapter.doProduce(WholeStageCodegenExec.scala:383)
            at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:88)
            at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:83)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
            at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
            at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
            at org.apache.spark.sql.execution.CodegenSupport$class.produce(WholeStageCodegenExec.scala:83)
            at org.apache.spark.sql.execution.InputAdapter.produce(WholeStageCodegenExec.scala:354)
            at org.apache.spark.sql.execution.ProjectExec.doProduce(basicPhysicalOperators.scala:45)
            at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:88)
            at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:83)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
            at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
            at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
            at org.apache.spark.sql.execution.CodegenSupport$class.produce(WholeStageCodegenExec.scala:83)
            at org.apache.spark.sql.execution.ProjectExec.produce(basicPhysicalOperators.scala:35)
            at org.apache.spark.sql.execution.WholeStageCodegenExec.doCodeGen(WholeStageCodegenExec.scala:524)
            at org.apache.spark.sql.execution.WholeStageCodegenExec.doExecute(WholeStageCodegenExec.scala:576)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:131)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:127)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
            at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
            at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
            at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:127)
            at org.apache.spark.sql.execution.DeserializeToObjectExec.doExecute(objects.scala:89)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:131)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:127)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
            at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
            at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
            at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:127)
            at org.apache.spark.sql.execution.QueryExecution.toRdd$lzycompute(QueryExecution.scala:80)
            at org.apache.spark.sql.execution.QueryExecution.toRdd(QueryExecution.scala:80)
            at org.apache.spark.sql.Dataset.rdd$lzycompute(Dataset.scala:2975)
            at org.apache.spark.sql.Dataset.rdd(Dataset.scala:2973)
            at org.apache.spark.sql.cassandra.CassandraSourceRelation.insert(CassandraSourceRelation.scala:76)
            at org.apache.spark.sql.cassandra.DefaultSource.createRelation(DefaultSource.scala:86)
            at org.apache.spark.sql.execution.datasources.SaveIntoDataSourceCommand.run(SaveIntoDataSourceCommand.scala:45)
            at org.apache.spark.sql.execution.command.ExecutedCommandExec.sideEffectResult$lzycompute(commands.scala:70)
            at org.apache.spark.sql.execution.command.ExecutedCommandExec.sideEffectResult(commands.scala:68)
            at org.apache.spark.sql.execution.command.ExecutedCommandExec.doExecute(commands.scala:86)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:131)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:127)
            at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
            at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
            at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
            at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:127)
            at org.apache.spark.sql.execution.QueryExecution.toRdd$lzycompute(QueryExecution.scala:80)
            at org.apache.spark.sql.execution.QueryExecution.toRdd(QueryExecution.scala:80)
            at org.apache.spark.sql.DataFrameWriter$$anonfun$runCommand$1.apply(DataFrameWriter.scala:654)
            at org.apache.spark.sql.DataFrameWriter$$anonfun$runCommand$1.apply(DataFrameWriter.scala:654)
            at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:77)
            at org.apache.spark.sql.DataFrameWriter.runCommand(DataFrameWriter.scala:654)
            at org.apache.spark.sql.DataFrameWriter.saveToV1Source(DataFrameWriter.scala:273)
            at org.apache.spark.sql.DataFrameWriter.save(DataFrameWriter.scala:267)
            at com.test.functions.package$ChecksFunctions.appendToTable(package.scala:66)
            at com.test.TestFromCassandra$.main(TestFromCassandra.scala:66)
            at com.test.TestFromCassandra.main(TestFromCassandra.scala)
            at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
            at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
            at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
            at java.lang.reflect.Method.invoke(Method.java:498)
            at org.apache.spark.deploy.JavaMainApplication.start(SparkApplication.scala:52)
            at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:894)
            at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:198)
            at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:228)
            at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:137)
            at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)
    2018-10-08 12:02:31 INFO  CassandraConnector:35 - Disconnected from Cassandra cluster: Test Cluster

TestFromCassandra文件的行号130是save()函数的调用。我在Stackoverflow上没有发现任何类似的问题。

有人知道我为什么遇到此异常吗？ lag函数对滚动sum函数是否有任何限制？

编辑： 我在Spark的Jira上找到了a similar issue。引用filter函数后，window函数似乎存在错误，并且由于cassandra连接器在过滤主键成员的数据帧之前（使用isnotnull函数）保存它，这可能会导致异常。 有没有一种方法可以通过避免此错误来执行此操作，但不使用聚合函数？还是有人知道如何解决此错误？

编辑2： 我还尝试使用foreach编写器和连接器withSessionDo函数存储数据框，但仍然遇到相同的异常。没有人遇到过此问题吗？

编辑3： 我找到了实现所需操作的另一种方法：

val leadWindow = Window.partitionBy(col("id")).orderBy(col("timestamp").desc).rowsBetween(Window.currentRow,, 2)
df.withColumn("lead1", sum(col("temp1")).over(leadWindow))

问题不是由于过滤器引起的。似乎不可能在窗口表达式上使用lag函数。

Answer 1

我看到了相同的错误。尽管有解决此问题的方法，但是spark应该可以解决此问题。我相信您会使用任何窗口功能（而不仅仅是LAG）来解决此问题。我相信原因是spark尝试在过滤器上执行代码生成，但是窗口函数无法代码生成。一种解决方法是使用此窗口表达式创建一列，然后在过滤器中使用该列。

Answer 2

我遇到了同样的问题，然后我注意到您正在使用lag内部的over函数（与我相同）。我变成了这样的东西：

df.withColumn("lag1", lag(sum(col("temp1")), 2, 0).over(lagWindow))