address the conflicts of two rules: PushPredicateThroughProject and PushProjectThroughFilter.

Author: gatorsmile

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala

@@ -65,11 +65,12 @@ abstract class Optimizer extends RuleExecutor[LogicalPlan] {
       SamplePushDown,
       ReorderJoin,
       OuterJoinElimination,
-      PushPredicateThroughJoin,
       PushPredicateThroughProject,
+      PushPredicateThroughJoin,
       PushPredicateThroughGenerate,
       PushPredicateThroughAggregate,
       LimitPushDown,
+      PushProjectThroughFilter,
       ColumnPruning,
       EliminateOperators,
       // Operator combine
@@ -91,6 +92,10 @@ abstract class Optimizer extends RuleExecutor[LogicalPlan] {
       SimplifyCasts,
       SimplifyCaseConversionExpressions,
       EliminateSerialization) ::
+    // Because ColumnPruning is called after PushPredicateThroughProject, the predicate push down
+    // is reversed. This batch is to ensure Filter is pushed below Project, if possible.
+    Batch("Push Predicate Through Project", Once,
+      PushPredicateThroughProject) ::
     Batch("Decimal Optimizations", FixedPoint(100),
       DecimalAggregates) ::
     Batch("LocalRelation", FixedPoint(100),
@@ -306,14 +311,28 @@ object SetOperationPushDown extends Rule[LogicalPlan] with PredicateHelper {
 }
 
 /**
- * Attempts to eliminate the reading of unneeded columns from the query plan using the following
- * transformations:
+ * Attempts to eliminate the reading of unneeded columns from the query plan
+ * by pushing Project through Filter.
  *
- *  - Inserting Projections beneath the following operators:
- *   - Aggregate
- *   - Generate
- *   - Project <- Join
- *   - LeftSemiJoin
+ * Note: This rule could reverse the effects of PushPredicateThroughProject.
+ * This rule should be run before ColumnPruning for ensuring that Project can be
+ * pushed as low as possible.
+ */
+object PushProjectThroughFilter extends Rule[LogicalPlan] {
+  def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
+    case p @ Project(projectList, f: Filter)
+        if f.condition.deterministic && projectList.forall(_.deterministic) =>
+      val required = f.references ++ p.references
+      if ((f.inputSet -- required).nonEmpty) {
+        p.copy(child = f.copy(child = ColumnPruning.prunedChild(f.child, required)))
+      } else {
+        p
+      }
+  }
+}
+
+/**
+ * Attempts to eliminate the reading of unneeded columns from the query plan
  */
 object ColumnPruning extends Rule[LogicalPlan] {
   def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
@@ -392,7 +411,7 @@ object ColumnPruning extends Rule[LogicalPlan] {
   }
 
   /** Applies a projection only when the child is producing unnecessary attributes */
-  private def prunedChild(c: LogicalPlan, allReferences: AttributeSet) =
+  def prunedChild(c: LogicalPlan, allReferences: AttributeSet): LogicalPlan =
     if ((c.outputSet -- allReferences.filter(c.outputSet.contains)).nonEmpty) {
       Project(c.output.filter(allReferences.contains), c)
     } else {
@@ -874,6 +893,10 @@ object PruneFilters extends Rule[LogicalPlan] with PredicateHelper {
  * that were defined in the projection.
  *
  * This heuristic is valid assuming the expression evaluation cost is minimal.
+ *
+ * Note: Because PushProjectThroughFilter could reverse the effect of PushPredicateThroughProject,
+ * PushPredicateThroughProject needs to be called before the other Predicate Push Down rules for
+ * ensuring the predicates can be pushed as low as possible.
  */
 object PushPredicateThroughProject extends Rule[LogicalPlan] with PredicateHelper {
   def apply(plan: LogicalPlan): LogicalPlan = plan transform {

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ColumnPruningSuite.scala

@@ -34,6 +34,9 @@ class ColumnPruningSuite extends PlanTest {
 
   object Optimize extends RuleExecutor[LogicalPlan] {
     val batches = Batch("Column pruning", FixedPoint(100),
+      PushPredicateThroughProject,
+      PushPredicateThroughJoin,
+      PushProjectThroughFilter,
       ColumnPruning,
       EliminateOperators,
       CollapseProject) :: Nil