[SPARK-27331] Schema mismatch using MicroBatchReader with columns pruning

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Invalid
• Affects Version/s: 2.3.1
• Component/s: Spark Core
• Labels: datasource

Environment

spark 2.3.1

• Assignee: Unassigned
• Reporter: Kineret
• Created: 31/Mar/19 10:27
• Updated: 12/Dec/22 18:11
• Resolved: 25/Apr/19 08:53

Description

I'm writing a custom Spark streaming source. I want to support columns pruning, I did something like this:

 

class MyMicroBatchReader(...) extends MicroBatchReader with SupportsPushDownRequiredColumns {

  var schema: StructType = createSchema()

  def readSchema(): StructType = schema

  def pruneColumns(requiredSchema: StructType): Unit = {
    schema = requiredSchema
  }

  ...

}

 

if I run a streaming query selecting some columns, the job fails. For example, running:

spark.readStream().format("mysource").load().select("Id").writeStream().format("console").start()

I obtain the following exception (in the second iteration):

18/06/29 15:50:01 ERROR MicroBatchExecution: Query [id = 59c13195-9d63-42c9-8f92-eb9d67e8b26c, runId = 72124019-1ab3-48a9-9503-0cf1c7d26fb9] terminated with error java.lang.AssertionError: assertion failed: Invalid batch: fieldA#0,fieldB#1,fieldC,Id#3,fieldD#4,fieldE#5 != Id#52 at scala.Predef$.assert(Predef.scala:170) at org.apache.spark.sql.execution.streaming.MicroBatchExecution$$anonfun$2$$anonfun$applyOrElse$4.apply(MicroBatchExecution.scala:417) at org.apache.spark.sql.execution.streaming.MicroBatchExecution$$anonfun$2$$anonfun$applyOrElse$4.apply(MicroBatchExecution.scala:416) at scala.Option.map(Option.scala:146) at org.apache.spark.sql.execution.streaming.MicroBatchExecution$$anonfun$2.applyOrElse(MicroBatchExecution.scala:416) at org.apache.spark.sql.execution.streaming.MicroBatchExecution$$anonfun$2.applyOrElse(MicroBatchExecution.scala:414) at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$2.apply(TreeNode.scala:267) at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$2.apply(TreeNode.scala:267) at org.apache.spark.sql.catalyst.trees.CurrentOrigin$.withOrigin(TreeNode.scala:70) at org.apache.spark.sql.catalyst.trees.TreeNode.transformDown(TreeNode.scala:266) at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$transformDown$1.apply(TreeNode.scala:272) at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$transformDown$1.apply(TreeNode.scala:272) at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$4.apply(TreeNode.scala:306) at org.apache.spark.sql.catalyst.trees.TreeNode.mapProductIterator(TreeNode.scala:187) at org.apache.spark.sql.catalyst.trees.TreeNode.mapChildren(TreeNode.scala:304) at org.apache.spark.sql.catalyst.trees.TreeNode.transformDown(TreeNode.scala:272) at org.apache.spark.sql.catalyst.trees.TreeNode.transform(TreeNode.scala:256) at org.apache.spark.sql.execution.streaming.MicroBatchExecution.org$apache$spark$sql$execution$streaming$MicroBatchExecution$$runBatch(MicroBatchExecution.scala:414) at org.apache.spark.sql.execution.streaming.MicroBatchExecution$$anonfun$runActivatedStream$1$$anonfun$apply$mcZ$sp$1.apply$mcV$sp(MicroBatchExecution.scala:133) at org.apache.spark.sql.execution.streaming.MicroBatchExecution$$anonfun$runActivatedStream$1$$anonfun$apply$mcZ$sp$1.apply(MicroBatchExecution.scala:121) at org.apache.spark.sql.execution.streaming.MicroBatchExecution$$anonfun$runActivatedStream$1$$anonfun$apply$mcZ$sp$1.apply(MicroBatchExecution.scala:121) at org.apache.spark.sql.execution.streaming.ProgressReporter$class.reportTimeTaken(ProgressReporter.scala:271) at org.apache.spark.sql.execution.streaming.StreamExecution.reportTimeTaken(StreamExecution.scala:58) at org.apache.spark.sql.execution.streaming.MicroBatchExecution$$anonfun$runActivatedStream$1.apply$mcZ$sp(MicroBatchExecution.scala:121) at org.apache.spark.sql.execution.streaming.ProcessingTimeExecutor.execute(TriggerExecutor.scala:56) at org.apache.spark.sql.execution.streaming.MicroBatchExecution.runActivatedStream(MicroBatchExecution.scala:117) at org.apache.spark.sql.execution.streaming.StreamExecution.org$apache$spark$sql$execution$streaming$StreamExecution$$runStream(StreamExecution.scala:279) at org.apache.spark.sql.execution.streaming.StreamExecution$$anon$1.run(StreamExecution.scala:189)

Can you please help?