[jira] [Created] (SPARK-23986) CompileException when using too many avg aggregation after joining

["Michel Davit (JIRA)" <ji...@apache.org>]

Michel Davit created SPARK-23986:
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             Summary: CompileException when using too many avg aggregation after joining
                 Key: SPARK-23986
                 URL: https://issues.apache.org/jira/browse/SPARK-23986
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 2.3.0
            Reporter: Michel Davit


Considering the following code:
{code:java}
    val df1: DataFrame = sparkSession.sparkContext
      .makeRDD(Seq((0, 1, 2, 3, 4, 5, 6)))
      .toDF("key", "col1", "col2", "col3", "col4", "col5", "col6")

    val df2: DataFrame = sparkSession.sparkContext
      .makeRDD(Seq((0, "val1", "val2")))
      .toDF("key", "dummy1", "dummy2")

    val agg = df1
      .join(df2, df1("key") === df2("key"), "leftouter")
      .groupBy(df1("key"))
      .agg(
        avg("col2").as("avg2"),
        avg("col3").as("avg3"),
        avg("col4").as("avg4"),
        avg("col1").as("avg1"),
        avg("col5").as("avg5"),
        avg("col6").as("avg6")
      )

    val head = agg.take(1)
{code}
This logs the following exception:
{code:java}
ERROR CodeGenerator: failed to compile: org.codehaus.commons.compiler.CompileException: File 'generated.java', Line 467, Column 28: Redefinition of parameter "agg_expr_11"
{code}
I am not a spark expert but after investigation, I realized that the generated {{doConsume}} method is responsible of the exception.

Indeed, {{avg}} calls several times {{org.apache.spark.sql.execution.CodegenSupport.constructDoConsumeFunction}}. The 1st time with the 'avg' Expr and a second time for the base aggregation Expr (count and sum).

The problem comes from the generation of parameters in CodeGenerator:
{code:java}
  /**
   * Returns a term name that is unique within this instance of a `CodegenContext`.
   */
  def freshName(name: String): String = synchronized {
    val fullName = if (freshNamePrefix == "") {
      name
    } else {
      s"${freshNamePrefix}_$name"
    }
    if (freshNameIds.contains(fullName)) {
      val id = freshNameIds(fullName)
      freshNameIds(fullName) = id + 1
      s"$fullName$id"
    } else {
      freshNameIds += fullName -> 1
      fullName
    }
  }
{code}
The {{freshNameIds}} already contains {{agg_expr_[1..6]}} from the 1st call.
 The second call is made with {{agg_expr_[1..12]}} and generates the following names:
 {{agg_expr_[11|21|31|41|51|61|11|12}}. We then have 2 parameter name conflicts in the generated code: {{agg_expr_11}} and {{agg_expr_12}}.

Appending the 'id' in s"$fullName$id" to generate unique term name is source of conflict. Maybe simply using undersoce can solve this issue : $fullName_$id"



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