[SPARK-10978] [SQL] Allow data sources to eliminate filters

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSourceStrategy.scala

@@ -43,7 +43,8 @@ private[sql] object DataSourceStrategy extends Strategy with Logging {
         l,
         projects,
         filters,
-        (a, f) => toCatalystRDD(l, a, t.buildScan(a, f))) :: Nil
+        (requestedColumns, allPredicates, _) =>
+          toCatalystRDD(l, requestedColumns, t.buildScan(requestedColumns, allPredicates))) :: Nil
 
     case PhysicalOperation(projects, filters, l @ LogicalRelation(t: PrunedFilteredScan, _)) =>
       pruneFilterProject(
@@ -266,47 +267,75 @@ private[sql] object DataSourceStrategy extends Strategy with Logging {
       relation,
       projects,
       filterPredicates,
-      (requestedColumns, pushedFilters) => {
-        scanBuilder(requestedColumns, selectFilters(pushedFilters).toArray)
+      (requestedColumns, _, pushedFilters) => {
+        scanBuilder(requestedColumns, pushedFilters.toArray)
       })
   }
 
-  // Based on Catalyst expressions.
+  // Based on Catalyst expressions. The `scanBuilder` function accepts three arguments:
+  //
+  //  1. A `Seq[Attribute]`, containing all required column attributes, used to handle traits like
+  //     `PrunedFilteredScan`.
+  //  2. A `Seq[Expression]`, containing all gathered Catalyst filter expressions, used by
+  //     `CatalystScan`.
+  //  3. A `Seq[Filter]`, containing all data source `Filter`s that are converted from (possibly a
+  //     subset of) Catalyst filter expressions and can be handled by `relation`.
   protected def pruneFilterProjectRaw(
-      relation: LogicalRelation,
-      projects: Seq[NamedExpression],
-      filterPredicates: Seq[Expression],
-      scanBuilder: (Seq[Attribute], Seq[Expression]) => RDD[InternalRow]) = {
+    relation: LogicalRelation,
+    projects: Seq[NamedExpression],
+    filterPredicates: Seq[Expression],
+    scanBuilder: (Seq[Attribute], Seq[Expression], Seq[Filter]) => RDD[InternalRow]) = {
 
     val projectSet = AttributeSet(projects.flatMap(_.references))
     val filterSet = AttributeSet(filterPredicates.flatMap(_.references))
-    val filterCondition = filterPredicates.reduceLeftOption(expressions.And)
 
-    val pushedFilters = filterPredicates.map { _ transform {
-      case a: AttributeReference => relation.attributeMap(a) // Match original case of attributes.
+    val candidatePredicates = filterPredicates.map { _ transform {
+        case a: AttributeReference => relation.attributeMap(a) // Match original case of attributes.
     }}
 
+    val (unhandledPredicates, pushedFilters) =
+      selectFilters(relation.relation, candidatePredicates)
+
+    // A set of column attributes that are only referenced by pushed down filters.  We can eliminate
+    // them from requested columns.
+    val handledSet = {
+      val handledPredicates = filterPredicates.filterNot(unhandledPredicates.contains)
+      val unhandledSet = AttributeSet(unhandledPredicates.flatMap(_.references))
+      AttributeSet(handledPredicates.flatMap(_.references)) --
+        (projectSet ++ unhandledSet).map(relation.attributeMap)
+    }
+
+    // Combines all Catalyst filter `Expression`s that are either not convertible to data source
+    // `Filter`s or cannot be handled by `relation`.
+    val filterCondition = unhandledPredicates.reduceLeftOption(expressions.And)
+
     if (projects.map(_.toAttribute) == projects &&
         projectSet.size == projects.size &&
         filterSet.subsetOf(projectSet)) {
       // When it is possible to just use column pruning to get the right projection and
       // when the columns of this projection are enough to evaluate all filter conditions,
       // just do a scan followed by a filter, with no extra project.
-      val requestedColumns =
-        projects.asInstanceOf[Seq[Attribute]] // Safe due to if above.
-          .map(relation.attributeMap)            // Match original case of attributes.
+      val requestedColumns = projects
+        // Safe due to if above.
+        .asInstanceOf[Seq[Attribute]]
+        // Match original case of attributes.
+        .map(relation.attributeMap)
+        // Don't request columns that are only referenced by pushed filters.
+        .filterNot(handledSet.contains)
 
       val scan = execution.PhysicalRDD.createFromDataSource(
         projects.map(_.toAttribute),
-        scanBuilder(requestedColumns, pushedFilters),
+        scanBuilder(requestedColumns, candidatePredicates, pushedFilters),
         relation.relation)
       filterCondition.map(execution.Filter(_, scan)).getOrElse(scan)
     } else {
-      val requestedColumns = (projectSet ++ filterSet).map(relation.attributeMap).toSeq
+      // Don't request columns that are only referenced by pushed filters.
+      val requestedColumns =
+        (projectSet ++ filterSet -- handledSet).map(relation.attributeMap).toSeq
 
       val scan = execution.PhysicalRDD.createFromDataSource(
         requestedColumns,
-        scanBuilder(requestedColumns, pushedFilters),
+        scanBuilder(requestedColumns, candidatePredicates, pushedFilters),
         relation.relation)
       execution.Project(projects, filterCondition.map(execution.Filter(_, scan)).getOrElse(scan))
     }
@@ -334,11 +363,12 @@ private[sql] object DataSourceStrategy extends Strategy with Logging {
   }
 
   /**
-   * Selects Catalyst predicate [[Expression]]s which are convertible into data source [[Filter]]s,
-   * and convert them.
+   * Tries to translate a Catalyst [[Expression]] into data source [[Filter]].
+   *
+   * @return a `Some[Filter]` if the input [[Expression]] is convertible, otherwise a `None`.
    */
-  protected[sql] def selectFilters(filters: Seq[Expression]) = {
-    def translate(predicate: Expression): Option[Filter] = predicate match {
+  protected[sql] def translateFilter(predicate: Expression): Option[Filter] = {
+    predicate match {
       case expressions.EqualTo(a: Attribute, Literal(v, t)) =>
         Some(sources.EqualTo(a.name, convertToScala(v, t)))
       case expressions.EqualTo(Literal(v, t), a: Attribute) =>
@@ -387,16 +417,16 @@ private[sql] object DataSourceStrategy extends Strategy with Logging {
         Some(sources.IsNotNull(a.name))
 
       case expressions.And(left, right) =>
-        (translate(left) ++ translate(right)).reduceOption(sources.And)
+        (translateFilter(left) ++ translateFilter(right)).reduceOption(sources.And)
 
       case expressions.Or(left, right) =>
         for {
-          leftFilter <- translate(left)
-          rightFilter <- translate(right)
+          leftFilter <- translateFilter(left)
+          rightFilter <- translateFilter(right)
         } yield sources.Or(leftFilter, rightFilter)
 
       case expressions.Not(child) =>
-        translate(child).map(sources.Not)
+        translateFilter(child).map(sources.Not)
 
       case expressions.StartsWith(a: Attribute, Literal(v: UTF8String, StringType)) =>
         Some(sources.StringStartsWith(a.name, v.toString))
@@ -409,7 +439,48 @@ private[sql] object DataSourceStrategy extends Strategy with Logging {
 
       case _ => None
     }
+  }
+
+  /**
+   * Selects Catalyst predicate [[Expression]]s which are convertible into data source [[Filter]]s
+   * and can be handled by `relation`.
+   *
+   * @return A pair of `Seq[Expression]` and `Seq[Filter]`. The first element contains all Catalyst
+   *         predicate [[Expression]]s that are either not convertible or cannot be handled by
+   *         `relation`. The second element contains all converted data source [[Filter]]s.
+   */
+  protected[sql] def selectFilters(
+    relation: BaseRelation,
+    predicates: Seq[Expression]): (Seq[Expression], Seq[Filter]) = {
+
+    // For conciseness, all Catalyst filter expressions of type `expressions.Expression` below are
+    // called `predicate`s, while all data source filters of type `sources.Filter` are simply called
+    // `filter`s.
+
+    val translated: Seq[(Expression, Filter)] =
+      for {
+        predicate <- predicates
+        filter <- translateFilter(predicate)
+      } yield predicate -> filter
+
+    // A map from original Catalyst expressions to corresponding translated data source filters.
+    val translatedMap: Map[Expression, Filter] = translated.toMap
+
+    // Catalyst predicate expressions that cannot be translated to data source filters.
+    val unrecognizedPredicates = predicates.filterNot(translatedMap.contains)
+
+    // Data source filters that cannot be handled by `relation`
+    val unhandledFilters = relation.unhandledFilters(translatedMap.values.toArray).toSet
+
+    // Catalyst predicate expressions that can be translated to data source filters, but cannot be
+    // handled by `relation`.
+    val unhandledPredicates = for {
+      (predicate, filter) <- translated if unhandledFilters.contains(filter)
+    } yield predicate
+
+    // Translated data source filters, no matter `relation` can handle them or not
+    val (_, translatedFilters) = translated.unzip
 
-    filters.flatMap(translate)
+    (unrecognizedPredicates ++ unhandledPredicates, translatedFilters)
   }
 }

sql/core/src/main/scala/org/apache/spark/sql/sources/interfaces.scala

@@ -233,6 +233,15 @@ abstract class BaseRelation {
    * @since 1.4.0
    */
   def needConversion: Boolean = true
+
+  /**
+   * Given an array of [[Filter]]s, returns an array of [[Filter]]s that this data source relation
+   * cannot handle.  Spark SQL will apply all returned [[Filter]]s against rows returned by this
+   * data source relation.
+   *
+   * @since 1.6.0
+   */
+  def unhandledFilters(filters: Array[Filter]): Array[Filter] = filters
 }
 
 /**

sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFilterSuite.scala

@@ -59,7 +59,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
       }.flatten
       assert(analyzedPredicate.nonEmpty)
 
-      val selectedFilters = DataSourceStrategy.selectFilters(analyzedPredicate)
+      val selectedFilters = analyzedPredicate.flatMap(DataSourceStrategy.translateFilter)
       assert(selectedFilters.nonEmpty)
 
       selectedFilters.foreach { pred =>