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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