Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/16933#discussion_r104786298
--- Diff:
sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/CollapseRepartitionSuite.scala
---
@@ -32,47 +32,180 @@ class CollapseRepartitionSuite extends PlanTest {
val testRelation = LocalRelation('a.int, 'b.int)
+
+ test("collapse two adjacent coalesces into one") {
+ // Always respects the top coalesces amd removes useless coalesce
below coalesce
+ val query1 = testRelation
+ .coalesce(10)
+ .coalesce(20)
+ val query2 = testRelation
+ .coalesce(30)
+ .coalesce(20)
+
+ val optimized1 = Optimize.execute(query1.analyze)
+ val optimized2 = Optimize.execute(query2.analyze)
+
+ val correctAnswer = testRelation.coalesce(20).analyze
+
+ comparePlans(optimized1, correctAnswer)
+ comparePlans(optimized2, correctAnswer)
+ }
+
test("collapse two adjacent repartitions into one") {
- val query = testRelation
+ // Always respects the top repartition amd removes useless repartition
below repartition
+ val query1 = testRelation
+ .repartition(10)
+ .repartition(20)
+ val query2 = testRelation
+ .repartition(30)
+ .repartition(20)
+
+ val optimized1 = Optimize.execute(query1.analyze)
+ val optimized2 = Optimize.execute(query2.analyze)
+ val correctAnswer = testRelation.repartition(20).analyze
+
+ comparePlans(optimized1, correctAnswer)
+ comparePlans(optimized2, correctAnswer)
+ }
+
+ test("coalesce above repartition") {
+ // Remove useless coalesce above repartition
+ val query1 = testRelation
.repartition(10)
+ .coalesce(20)
+
+ val optimized1 = Optimize.execute(query1.analyze)
+ val correctAnswer1 = testRelation.repartition(10).analyze
+
+ comparePlans(optimized1, correctAnswer1)
+
+ // No change in this case
+ val query2 = testRelation
+ .repartition(30)
+ .coalesce(20)
+
+ val optimized2 = Optimize.execute(query2.analyze)
+ val correctAnswer2 = query2.analyze
+
+ comparePlans(optimized2, correctAnswer2)
+ }
+
+ test("repartition above coalesce") {
+ // Always respects the top repartition amd removes useless coalesce
below repartition
+ val query1 = testRelation
+ .coalesce(10)
+ .repartition(20)
+ // Remove useless coalesce above repartition
+ val query2 = testRelation
+ .coalesce(30)
.repartition(20)
- val optimized = Optimize.execute(query.analyze)
+ val optimized1 = Optimize.execute(query1.analyze)
+ val optimized2 = Optimize.execute(query2.analyze)
+
val correctAnswer = testRelation.repartition(20).analyze
- comparePlans(optimized, correctAnswer)
+ comparePlans(optimized1, correctAnswer)
+ comparePlans(optimized2, correctAnswer)
}
- test("collapse repartition and repartitionBy into one") {
- val query = testRelation
+ test("repartitionBy above repartition") {
+ val query1 = testRelation
.repartition(10)
.distribute('a)(20)
- val optimized = Optimize.execute(query.analyze)
- val correctAnswer = testRelation.distribute('a)(20).analyze
+ val optimized1 = Optimize.execute(query1.analyze)
+ val correctAnswer1 = testRelation.distribute('a)(20).analyze
+
+ comparePlans(optimized1, correctAnswer1)
+
+ val query2 = testRelation
+ .repartition(30)
+ .distribute('a)(20)
+
+ val optimized2 = Optimize.execute(query2.analyze)
+ val correctAnswer2 = testRelation.distribute('a)(20).analyze
- comparePlans(optimized, correctAnswer)
+ comparePlans(optimized2, correctAnswer2)
}
- test("collapse repartitionBy and repartition into one") {
- val query = testRelation
+ test("repartitionBy above coalesce") {
+ val query1 = testRelation
+ .coalesce(10)
+ .distribute('a)(20)
+
+ val optimized1 = Optimize.execute(query1.analyze)
+ val correctAnswer1 = testRelation.distribute('a)(20).analyze
+
+ comparePlans(optimized1, correctAnswer1)
+
+ val query2 = testRelation
+ .coalesce(20)
+ .distribute('a)(30)
+
+ val optimized2 = Optimize.execute(query2.analyze)
+ val correctAnswer2 = testRelation.distribute('a)(30).analyze
+
+ comparePlans(optimized2, correctAnswer2)
+ }
+
+ test("repartition above repartitionBy") {
+ val query1 = testRelation
.distribute('a)(20)
.repartition(10)
- val optimized = Optimize.execute(query.analyze)
- val correctAnswer = testRelation.distribute('a)(10).analyze
+ val optimized1 = Optimize.execute(query1.analyze)
+ val correctAnswer1 = testRelation.distribute('a)(10).analyze
--- End diff --
Here, I just followed what we did before. After more code reading, I think
we can do it, since `RoundRobinPartitioning ` looks cheaper.
```Scala
case logical.Repartition(numPartitions, shuffle, child) =>
if (shuffle) {
ShuffleExchange(RoundRobinPartitioning(numPartitions),
planLater(child)) :: Nil
} else {
execution.CoalesceExec(numPartitions, planLater(child)) :: Nil
}
case logical.RepartitionByExpression(expressions, child,
numPartitions) =>
exchange.ShuffleExchange(HashPartitioning(
expressions, numPartitions), planLater(child)) :: Nil
```
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