Use spark sql optimizer to optimize two ranges join

[bithw1]

Hi @bartosz25 ,

I got a question that I would like you to help take a look, thank you.

I want to use spark sql optimizer to optimize two ranges join , just to calculate two range intersection,so that it can avoid join

test("SparkTest") {
    object RangeIntersectRule extends Rule[LogicalPlan] {
      override def apply(plan: LogicalPlan): LogicalPlan = plan transformDown {
        case Join(Project(_, Range(start1, end1, _, _, _, _)), Project(_, Range(start2, end2, _, _, _, _)), _, _) => {
          val start = start1 max start2
          val end = end1 min end2
          if (start1 > end2 || end1 < start2) Range(0, 0, 1, Some(1), false) else Range(start, end, 1, Some(1), false)


        }
      }
    }

    val spark = SparkSession.builder().master("local").appName("SparkTest").enableHiveSupport().getOrCreate()
    spark.experimental.extraOptimizations = Seq(RangeIntersectRule)
    spark.range(10, 40).toDF("x").createOrReplaceTempView("t1")
    spark.range(20, 50).toDF("y").createOrReplaceTempView("t2")
    val df = spark.sql("select t1.x from t1 join t2 on t1.x = t2.y")
    df.explain(true)
    df.show(truncate = false)
  }

The rule takes effect, but it throws exception as follows, looks I haven't implemented the apply method appropriately

The plan is

== Parsed Logical Plan ==
'Project [UnresolvedAttribute_'t1.x]
+- 'Join Inner, (UnresolvedAttribute_'t1.x = UnresolvedAttribute_'t2.y)
   :- 'UnresolvedRelation `t1`
   +- 'UnresolvedRelation `t2`

== Analyzed Logical Plan ==
x: bigint
Project [x#2L]
+- Join Inner, (x#2L = y#6L)
   :- SubqueryAlias `t1`
   :  +- Project [id#0L AS x#2L]
   :     +- Range (10, 40, step=1, splits=Some(1))
   +- SubqueryAlias `t2`
      +- Project [id#4L AS y#6L]
         +- Range (20, 50, step=1, splits=Some(1))

== Optimized Logical Plan ==
!Project [x#2L]
+- Range (20, 40, step=1, splits=Some(1))

== Physical Plan ==
!Project [x#2L]
+- Range (20, 40, step=1, splits=1)

The exception is:

Caused by: java.lang.RuntimeException: Couldn't find x#2L in [id#14L]
	at scala.sys.package$.error(package.scala:27)
	at org.apache.spark.sql.catalyst.expressions.BindReferences$$anonfun$bindReference$1$$anonfun$applyOrElse$1.apply(BoundAttribute.scala:107)
	at org.apache.spark.sql.catalyst.expressions.BindReferences$$anonfun$bindReference$1$$anonfun$applyOrElse$1.apply(BoundAttribute.scala:101)
	at org.apache.spark.sql.catalyst.errors.package$.attachTree(package.scala:59)
	... 50 more

[bartosz25]

Hi @bithw1

I'll try to take a look today or tomorrow.

Best regards,
Bartosz.

[bartosz25]

@bithw1

The range method returns a DataFrame with a single one column called id. It's why the engines looks for it in your query declaration:

   * Creates a [[Dataset]] with a single `LongType` column named `id`, containing elements
   * in a range from `start` to `end` (exclusive) with step value 1.

If you rewrite your query like this it should work:

     val spark = SparkSession.builder().master("local").appName("SparkTest").enableHiveSupport().getOrCreate()
    spark.experimental.extraOptimizations = Seq(RangeIntersectRule)
    spark.range(10, 40).createOrReplaceTempView("t1")
    spark.range(20, 50).createOrReplaceTempView("t2")
    val df = spark.sql("select t1.id from t1 join t2 on t1.id = t2.id")
    df.explain(true)
    df.show(truncate = false)

Best regards,
Bartosz.

[bithw1]

Thanks @bartosz25 , but when rewriting it using column id, the rule doesn't take effect, you could see that the physical plan is still using BroadcastHashJoin.

When using id, I try to modify the rule'apply method, I still can't be able to make the apply method work ,still throwing
Caused by: java.lang.RuntimeException: Couldn't find id#0L in [id#2L]

    object RangeIntersectRule extends Rule[LogicalPlan] {
      override def apply(plan: LogicalPlan): LogicalPlan = plan transformDown {
        case Join(Range(start1, end1, 1, Some(1), output1, false), Range(start2, end2, 1, Some(1), output2, false), Inner, _) => {
          val start = start1 max start2
          val end = end1 min end2
          if (start1 > end2 || end1 < start2) Range(0, 0, 1, Some(1), output1, false)
          else Range(start, end, 1, Some(1), output1, false)
        }
      }
    }

[bithw1]

Hi @bartosz25

I wrap Range with Project as the following code does, it works but I have no idea why it should be wrapped with Project,could you please help take a look? thank you.

    object RangeIntersectRule extends Rule[LogicalPlan] {
      override def apply(plan: LogicalPlan): LogicalPlan = plan transformDown {
        case Join(Range(start1, end1, 1, Some(1), output1, false), Range(start2, end2, 1, Some(1), output2, false), Inner, _) => {
          val start = start1 max start2
          val end = end1 min end2
          if (start1 > end2 || end1 < start2) Project(output1, Range(0, 0, 1, Some(1), output1, false))
          //wrap Range with Project
          else Project(output1, Range(start, end, 1, Some(1), output1, false))
        }
      }
    }

[bartosz25]

Hi @bithw1

Sorry, I missed your message last week. I'll add the topic of extra optimizations to my backlog and try to answer your question here when I'll write about it.

Best regards,
Bartosz.

[bithw1]

Sure， thank you @bartosz25 !

[bartosz25]

Hi @bithw1

Today I started the topic of custom optimizations. Since the topic is quite new for me, I will go slowly from the basics and try to cover more advanced concepts at the end. The first post is there : https://www.waitingforcode.com/apache-spark-sql/introduction-custom-optimization-apache-spark-sql/read

Best regards,
Bartosz.

[bithw1]

That's great, thanks @bartosz25. Looking forward to your great posts and learn, :-)