[SPARK-16014][SQL] Rename optimizer rules to be more consistent

## What changes were proposed in this pull request?
This small patch renames a few optimizer rules to make the naming more consistent, e.g. class name start with a verb. The main important "fix" is probably SamplePushDown -> PushProjectThroughSample. SamplePushDown is actually the wrong name, since the rule is not about pushing Sample down.

## How was this patch tested?
Updated test cases.

Author: Reynold Xin <rxin@databricks.com>

Closes #13732 from rxin/SPARK-16014.

6 files changed, 19 insertions, 22 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/DistinctAggregationRewriter.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/RewriteDistinctAggregates.scala
index 063eff4f98..8afd28dbba 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/DistinctAggregationRewriter.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/RewriteDistinctAggregates.scala
@@ -99,7 +99,7 @@ import org.apache.spark.sql.types.IntegerType
  * we could improve this in the current rule by applying more advanced expression canonicalization
  * techniques.
  */
-object DistinctAggregationRewriter extends Rule[LogicalPlan] {
+object RewriteDistinctAggregates extends Rule[LogicalPlan] {
 
   def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
     case a: Aggregate => rewrite(a)
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
index 7b9b21f416..6e78ad0e77 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
@@ -52,7 +52,7 @@ abstract class Optimizer(sessionCatalog: SessionCatalog, conf: CatalystConf)
       ReplaceExpressions,
       ComputeCurrentTime,
       GetCurrentDatabase(sessionCatalog),
-      DistinctAggregationRewriter) ::
+      RewriteDistinctAggregates) ::
     //////////////////////////////////////////////////////////////////////////////////////////
     // Optimizer rules start here
     //////////////////////////////////////////////////////////////////////////////////////////
@@ -74,10 +74,10 @@ abstract class Optimizer(sessionCatalog: SessionCatalog, conf: CatalystConf)
       RemoveRepetitionFromGroupExpressions) ::
     Batch("Operator Optimizations", fixedPoint,
       // Operator push down
-      SetOperationPushDown,
-      SamplePushDown,
+      PushThroughSetOperations,
+      PushProjectThroughSample,
       ReorderJoin,
-      OuterJoinElimination,
+      EliminateOuterJoin,
       PushPredicateThroughJoin,
       PushDownPredicate,
       LimitPushDown,
@@ -99,7 +99,7 @@ abstract class Optimizer(sessionCatalog: SessionCatalog, conf: CatalystConf)
       BooleanSimplification,
       SimplifyConditionals,
       RemoveDispensableExpressions,
-      BinaryComparisonSimplification,
+      SimplifyBinaryComparison,
       PruneFilters,
       EliminateSorts,
       SimplifyCasts,
@@ -148,10 +148,9 @@ class SimpleTestOptimizer extends Optimizer(
   new SimpleCatalystConf(caseSensitiveAnalysis = true))
 
 /**
- * Pushes operations down into a Sample.
+ * Pushes projects down beneath Sample to enable column pruning with sampling.
  */
-object SamplePushDown extends Rule[LogicalPlan] {
-
+object PushProjectThroughSample extends Rule[LogicalPlan] {
   def apply(plan: LogicalPlan): LogicalPlan = plan transform {
     // Push down projection into sample
     case Project(projectList, Sample(lb, up, replace, seed, child)) =>
@@ -171,7 +170,7 @@ object RemoveAliasOnlyProject extends Rule[LogicalPlan] {
       projectList: Seq[NamedExpression],
       childOutput: Seq[Attribute]): Boolean = {
     if (!projectList.forall(_.isInstanceOf[Alias]) || projectList.length != childOutput.length) {
-      return false
+      false
     } else {
       projectList.map(_.asInstanceOf[Alias]).zip(childOutput).forall { case (a, o) =>
         a.child match {
@@ -183,11 +182,9 @@ object RemoveAliasOnlyProject extends Rule[LogicalPlan] {
   }
 
   def apply(plan: LogicalPlan): LogicalPlan = {
-    val aliasOnlyProject = plan.find { p =>
-      p match {
-        case Project(pList, child) if isAliasOnly(pList, child.output) => true
-        case _ => false
-      }
+    val aliasOnlyProject = plan.find {
+      case Project(pList, child) if isAliasOnly(pList, child.output) => true
+      case _ => false
     }
 
     aliasOnlyProject.map { case p: Project =>
@@ -292,7 +289,7 @@ object LimitPushDown extends Rule[LogicalPlan] {
  * safe to pushdown Filters and Projections through it. Once we add UNION DISTINCT,
  * we will not be able to pushdown Projections.
  */
-object SetOperationPushDown extends Rule[LogicalPlan] with PredicateHelper {
+object PushThroughSetOperations extends Rule[LogicalPlan] with PredicateHelper {
 
   /**
    * Maps Attributes from the left side to the corresponding Attribute on the right side.
@@ -918,7 +915,7 @@ object BooleanSimplification extends Rule[LogicalPlan] with PredicateHelper {
  * 2) Replace '=', '<=', and '>=' with 'true' literal if both operands are non-nullable.
  * 3) Replace '<' and '>' with 'false' literal if both operands are non-nullable.
  */
-object BinaryComparisonSimplification extends Rule[LogicalPlan] with PredicateHelper {
+object SimplifyBinaryComparison extends Rule[LogicalPlan] with PredicateHelper {
   def apply(plan: LogicalPlan): LogicalPlan = plan transform {
     case q: LogicalPlan => q transformExpressionsUp {
       // True with equality
@@ -1256,7 +1253,7 @@ object ReorderJoin extends Rule[LogicalPlan] with PredicateHelper {
  *
  * This rule should be executed before pushing down the Filter
  */
-object OuterJoinElimination extends Rule[LogicalPlan] with PredicateHelper {
+object EliminateOuterJoin extends Rule[LogicalPlan] with PredicateHelper {
 
   /**
    * Returns whether the expression returns null or false when all inputs are nulls.
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/BinaryComparisonSimplificationSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/BinaryComparisonSimplificationSuite.scala
index 7cd038570b..a313681eeb 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/BinaryComparisonSimplificationSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/BinaryComparisonSimplificationSuite.scala
@@ -36,7 +36,7 @@ class BinaryComparisonSimplificationSuite extends PlanTest with PredicateHelper
         NullPropagation,
         ConstantFolding,
         BooleanSimplification,
-        BinaryComparisonSimplification,
+        SimplifyBinaryComparison,
         PruneFilters) :: Nil
   }
 
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/FilterPushdownSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/FilterPushdownSuite.scala
index fcc14a803b..b8f28e83e7 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/FilterPushdownSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/FilterPushdownSuite.scala
@@ -34,7 +34,7 @@ class FilterPushdownSuite extends PlanTest {
       Batch("Subqueries", Once,
         EliminateSubqueryAliases) ::
       Batch("Filter Pushdown", FixedPoint(10),
-        SamplePushDown,
+        PushProjectThroughSample,
         CombineFilters,
         PushDownPredicate,
         BooleanSimplification,
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/OuterJoinEliminationSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/OuterJoinEliminationSuite.scala
index 5e6e54dc74..41754adef4 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/OuterJoinEliminationSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/OuterJoinEliminationSuite.scala
@@ -30,7 +30,7 @@ class OuterJoinEliminationSuite extends PlanTest {
       Batch("Subqueries", Once,
         EliminateSubqueryAliases) ::
       Batch("Outer Join Elimination", Once,
-        OuterJoinElimination,
+        EliminateOuterJoin,
         PushPredicateThroughJoin) :: Nil
   }
 
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/SetOperationSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/SetOperationSuite.scala
index 83ca9d5ec9..dab45a6b16 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/SetOperationSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/SetOperationSuite.scala
@@ -31,7 +31,7 @@ class SetOperationSuite extends PlanTest {
         EliminateSubqueryAliases) ::
       Batch("Union Pushdown", Once,
         CombineUnions,
-        SetOperationPushDown,
+        PushThroughSetOperations,
         PruneFilters) :: Nil
   }