Github user HyukjinKwon commented on the issue:
https://github.com/apache/spark/pull/20856
Okay, I was investigating this and the fix itself looks quite inappropriate.
This looks what happened now. I can reproduce this by a bit of messy way:
```diff
diff --git
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
index 8d06804ce1e..d25fc9a7ba9 100644
---
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
+++
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
@@ -37,7 +37,9 @@ class EquivalentExpressions {
case _ => false
}
- override def hashCode: Int = e.semanticHash()
+ override def hashCode: Int = {
+ 1
+ }
}
```
```scala
spark.range(1).write.mode("overwrite").parquet("/tmp/foo")
spark.read.parquet("/tmp/foo").createOrReplaceTempView("foo")
spark.conf.set("spark.sql.codegen.wholeStage", false)
sql("SELECT (SELECT id FROM foo) == (SELECT id FROM foo)").collect()
```
This is what I see and think:
1. Sub scalar query was made (for instance `SELECT (SELECT id FROM foo)`).
2. Try to extract some common expressions (via
`CodeGenerator.subexpressionElimination`) so that it can generates some common
codes and can be reused.
3. During this, seems it extracts some expressions that can be reused (via
`EquivalentExpressions.addExprTree`)
https://github.com/apache/spark/blob/b2deef64f604ddd9502a31105ed47cb63470ec85/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala#L1102
4. During this, if the hash (`EquivalentExpressions.Expr.hashCode`)
happened to be the same at `EquivalentExpressions.addExpr`
anyhow,â`EquivalentExpressions.Expr.equals` is called to identicy object in
the same hash, which eventually calls `semanticEquals` in `ScalarSubquery`
https://github.com/apache/spark/blob/087879a77acb37b790c36f8da67355b90719c2dc/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala#L54
https://github.com/apache/spark/blob/087879a77acb37b790c36f8da67355b90719c2dc/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala#L36
5. `ScalarSubquery`'s `semanticEquals` needs `SubqueryExec`'s `sameResult`
https://github.com/apache/spark/blob/77a2fc5b521788b406bb32bcc3c637c1d7406e58/sql/core/src/main/scala/org/apache/spark/sql/execution/subquery.scala#L58
6. `SubqueryExec`'s `sameResult` requires a canonicalized plan which calls
`FileSourceScanExec`'s `doCanonicalize`
https://github.com/apache/spark/blob/e008ad175256a3192fdcbd2c4793044d52f46d57/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala#L258
7. In `FileSourceScanExec`'s `doCanonicalize`, `FileSourceScanExec`'s
`relation` is required but seems `@transient` so it becomes `null`.
https://github.com/apache/spark/blob/e76b0124fbe463def00b1dffcfd8fd47e04772fe/sql/core/src/main/scala/org/apache/spark/sql/execution/DataSourceScanExec.scala#L527
https://github.com/apache/spark/blob/e76b0124fbe463def00b1dffcfd8fd47e04772fe/sql/core/src/main/scala/org/apache/spark/sql/execution/DataSourceScanExec.scala#L160
8. NPE is thrown:
```
java.lang.NullPointerException
at
org.apache.spark.sql.execution.FileSourceScanExec.<init>(DataSourceScanExec.scala:169)
at
org.apache.spark.sql.execution.FileSourceScanExec.doCanonicalize(DataSourceScanExec.scala:526)
at
org.apache.spark.sql.execution.FileSourceScanExec.doCanonicalize(DataSourceScanExec.scala:159)
at
org.apache.spark.sql.catalyst.plans.QueryPlan.canonicalized$lzycompute(QueryPlan.scala:211)
at
org.apache.spark.sql.catalyst.plans.QueryPlan.canonicalized(QueryPlan.scala:210)
at
org.apache.spark.sql.catalyst.plans.QueryPlan$$anonfun$3.apply(QueryPlan.scala:225)
at
org.apache.spark.sql.catalyst.plans.QueryPlan$$anonfun$3.apply(QueryPlan.scala:225)
at
scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
at
scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
at scala.collection.immutable.List.foreach(List.scala:392)
at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
at scala.collection.immutable.List.map(List.scala:296)
at
org.apache.spark.sql.catalyst.plans.QueryPlan.doCanonicalize(QueryPlan.scala:225)
at
org.apache.spark.sql.catalyst.plans.QueryPlan.canonicalized$lzycompute(QueryPlan.scala:211)
at
org.apache.spark.sql.catalyst.plans.QueryPlan.canonicalized(QueryPlan.scala:210)
at
org.apache.spark.sql.catalyst.plans.QueryPlan.sameResult(QueryPlan.scala:258)
at
org.apache.spark.sql.execution.ScalarSubquery.semanticEquals(subquery.scala:58)
at
org.apache.spark.sql.catalyst.expressions.EquivalentExpressions$Expr.equals(EquivalentExpressions.scala:36)
at
scala.collection.mutable.HashTable$class.elemEquals(HashTable.scala:364)
at scala.collection.mutable.HashMap.elemEquals(HashMap.scala:40)
at
scala.collection.mutable.HashTable$class.scala$collection$mutable$HashTable$$findEntry0(HashTable.scala:139)
at
scala.collection.mutable.HashTable$class.findEntry(HashTable.scala:135)
at scala.collection.mutable.HashMap.findEntry(HashMap.scala:40)
at scala.collection.mutable.HashMap.get(HashMap.scala:70)
at
org.apache.spark.sql.catalyst.expressions.EquivalentExpressions.addExpr(EquivalentExpressions.scala:56)
at
org.apache.spark.sql.catalyst.expressions.EquivalentExpressions.addExprTree(EquivalentExpressions.scala:97)
at
org.apache.spark.sql.catalyst.expressions.EquivalentExpressions$$anonfun$addExprTree$1.apply(EquivalentExpressions.scala:98)
at
org.apache.spark.sql.catalyst.expressions.EquivalentExpressions$$anonfun$addExprTree$1.apply(EquivalentExpressions.scala:98)
at scala.collection.immutable.List.foreach(List.scala:392)
at
org.apache.spark.sql.catalyst.expressions.EquivalentExpressions.addExprTree(EquivalentExpressions.scala:98)
at
org.apache.spark.sql.catalyst.expressions.codegen.CodegenContext$$anonfun$subexpressionElimination$1.apply(CodeGenerator.scala:1102)
at
org.apache.spark.sql.catalyst.expressions.codegen.CodegenContext$$anonfun$subexpressionElimination$1.apply(CodeGenerator.scala:1102)
at scala.collection.immutable.List.foreach(List.scala:392)
at
org.apache.spark.sql.catalyst.expressions.codegen.CodegenContext.subexpressionElimination(CodeGenerator.scala:1102)
at
org.apache.spark.sql.catalyst.expressions.codegen.CodegenContext.generateExpressions(CodeGenerator.scala:1154)
at
org.apache.spark.sql.catalyst.expressions.codegen.GenerateUnsafeProjection$.createCode(GenerateUnsafeProjection.scala:270)
at
org.apache.spark.sql.catalyst.expressions.codegen.GenerateUnsafeProjection$.create(GenerateUnsafeProjection.scala:319)
at
org.apache.spark.sql.catalyst.expressions.codegen.GenerateUnsafeProjection$.generate(GenerateUnsafeProjection.scala:308)
at
org.apache.spark.sql.catalyst.expressions.UnsafeProjection$.create(Projection.scala:181)
at
org.apache.spark.sql.execution.ProjectExec$$anonfun$9.apply(basicPhysicalOperators.scala:71)
at
org.apache.spark.sql.execution.ProjectExec$$anonfun$9.apply(basicPhysicalOperators.scala:70)
at
org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndexInternal$1$$anonfun$apply$24.apply(RDD.scala:818)
at
org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndexInternal$1$$anonfun$apply$24.apply(RDD.scala:818)
at
org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:288)
at
org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:288)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87)
at org.apache.spark.scheduler.Task.run(Task.scala:109)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:367)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
```
\*1. driver side
\*2., 3., 4., 5., 6., 7., 8. executor side
Note that most of cases, it looks fine because we will usually call:
https://github.com/apache/spark/blob/087879a77acb37b790c36f8da67355b90719c2dc/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala#L40
which make a canonicalized plan via:
https://github.com/apache/spark/blob/b045315e5d87b7ea3588436053aaa4d5a7bd103f/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala#L192
https://github.com/apache/spark/blob/77a2fc5b521788b406bb32bcc3c637c1d7406e58/sql/core/src/main/scala/org/apache/spark/sql/execution/subquery.scala#L52
I currently faced a bigger question. These canonicalized plans are meant to
be made in executor sides? cc @cloud-fan, @viirya , @mgaido91
Looks we are already doing so. Now looks we have incomplete
`FileSourceScanExec` on the executors.
Please correct me if I am competely mistaken somewhere.
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