[SPARK-5278][SQL] Introduce UnresolvedGetField and complete the check of ambiguous reference to fields

When the `GetField` chain(`a.b.c.d.....`) is interrupted by `GetItem` like `a.b[0].c.d....`, then the check of ambiguous reference to fields is broken.
The reason is that: for something like `a.b[0].c.d`, we first parse it to `GetField(GetField(GetItem(Unresolved("a.b"), 0), "c"), "d")`. Then in `LogicalPlan#resolve`, we resolve `"a.b"` and build a `GetField` chain from bottom(the relation). But for the 2 outer `GetFiled`, we have to resolve them in `Analyzer` or do it in `GetField` lazily, check data type of child, search needed field, etc. which is similar to what we have done in `LogicalPlan#resolve`.
So in this PR, the fix is just copy the same logic in `LogicalPlan#resolve` to `Analyzer`, which is simple and quick, but I do suggest introduce `UnresolvedGetFiled` like I explained in #2405.

Author: Wenchen Fan <[email protected]>

Closes #4068 from cloud-fan/simple and squashes the following commits:

a6857b5 [Wenchen Fan] fix import order
8411c40 [Wenchen Fan] use UnresolvedGetField

Author: cloud-fan

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala

@@ -372,7 +372,7 @@ class SqlParser extends AbstractSparkSQLParser {
     | expression ~ ("[" ~> expression <~ "]") ^^
       { case base ~ ordinal => GetItem(base, ordinal) }
     | (expression <~ ".") ~ ident ^^
-      { case base ~ fieldName => GetField(base, fieldName) }
+      { case base ~ fieldName => UnresolvedGetField(base, fieldName) }
     | cast
     | "(" ~> expression <~ ")"
     | function

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala

@@ -285,7 +285,7 @@ class Analyzer(catalog: Catalog,
 
       case q: LogicalPlan =>
         logTrace(s"Attempting to resolve ${q.simpleString}")
-        q transformExpressions {
+        q transformExpressionsUp  {
           case u @ UnresolvedAttribute(name) if resolver(name, VirtualColumn.groupingIdName) &&
             q.isInstanceOf[GroupingAnalytics] =>
             // Resolve the virtual column GROUPING__ID for the operator GroupingAnalytics
@@ -295,15 +295,8 @@ class Analyzer(catalog: Catalog,
             val result = q.resolveChildren(name, resolver).getOrElse(u)
             logDebug(s"Resolving $u to $result")
             result
-
-          // Resolve field names using the resolver.
-          case f @ GetField(child, fieldName) if !f.resolved && child.resolved =>
-            child.dataType match {
-              case StructType(fields) =>
-                val resolvedFieldName = fields.map(_.name).find(resolver(_, fieldName))
-                resolvedFieldName.map(n => f.copy(fieldName = n)).getOrElse(f)
-              case _ => f
-            }
+          case UnresolvedGetField(child, fieldName) if child.resolved =>
+            resolveGetField(child, fieldName)
         }
     }
 
@@ -312,6 +305,27 @@ class Analyzer(catalog: Catalog,
      */
     protected def containsStar(exprs: Seq[Expression]): Boolean =
       exprs.exists(_.collect { case _: Star => true }.nonEmpty)
+
+    /**
+     * Returns the resolved `GetField`, and report error if no desired field or over one
+     * desired fields are found.
+     */
+    protected def resolveGetField(expr: Expression, fieldName: String): Expression = {
+      expr.dataType match {
+        case StructType(fields) =>
+          val actualField = fields.filter(f => resolver(f.name, fieldName))
+          if (actualField.length == 0) {
+            sys.error(
+              s"No such struct field $fieldName in ${fields.map(_.name).mkString(", ")}")
+          } else if (actualField.length == 1) {
+            val field = actualField(0)
+            GetField(expr, field, fields.indexOf(field))
+          } else {
+            sys.error(s"Ambiguous reference to fields ${actualField.mkString(", ")}")
+          }
+        case otherType => sys.error(s"GetField is not valid on fields of type $otherType")
+      }
+    }
   }
 
   /**

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/unresolved.scala

@@ -177,3 +177,15 @@ case class ResolvedStar(expressions: Seq[NamedExpression]) extends Star {
   override def expand(input: Seq[Attribute], resolver: Resolver): Seq[NamedExpression] = expressions
   override def toString = expressions.mkString("ResolvedStar(", ", ", ")")
 }
+
+case class UnresolvedGetField(child: Expression, fieldName: String) extends UnaryExpression {
+  override def dataType = throw new UnresolvedException(this, "dataType")
+  override def foldable = throw new UnresolvedException(this, "foldable")
+  override def nullable = throw new UnresolvedException(this, "nullable")
+  override lazy val resolved = false
+
+  override def eval(input: Row = null): EvaluatedType =
+    throw new TreeNodeException(this, s"No function to evaluate expression. type: ${this.nodeName}")
+
+  override def toString = s"$child.$fieldName"
+}

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/dsl/package.scala

@@ -22,7 +22,7 @@ import java.sql.{Date, Timestamp}
 import scala.language.implicitConversions
 import scala.reflect.runtime.universe.{TypeTag, typeTag}
 
-import org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute
+import org.apache.spark.sql.catalyst.analysis.{UnresolvedGetField, UnresolvedAttribute}
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.logical._
 import org.apache.spark.sql.catalyst.plans.{Inner, JoinType}
@@ -101,7 +101,7 @@ package object dsl {
     def isNotNull = IsNotNull(expr)
 
     def getItem(ordinal: Expression) = GetItem(expr, ordinal)
-    def getField(fieldName: String) = GetField(expr, fieldName)
+    def getField(fieldName: String) = UnresolvedGetField(expr, fieldName)
 
     def cast(to: DataType) = Cast(expr, to)
 

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/complexTypes.scala

@@ -73,39 +73,19 @@ case class GetItem(child: Expression, ordinal: Expression) extends Expression {
 /**
  * Returns the value of fields in the Struct `child`.
  */
-case class GetField(child: Expression, fieldName: String) extends UnaryExpression {
+case class GetField(child: Expression, field: StructField, ordinal: Int) extends UnaryExpression {
   type EvaluatedType = Any
 
   def dataType = field.dataType
   override def nullable = child.nullable || field.nullable
   override def foldable = child.foldable
 
-  protected def structType = child.dataType match {
-    case s: StructType => s
-    case otherType => sys.error(s"GetField is not valid on fields of type $otherType")
-  }
-
-  lazy val field =
-    structType.fields
-        .find(_.name == fieldName)
-        .getOrElse(sys.error(s"No such field $fieldName in ${child.dataType}"))
-
-  lazy val ordinal = structType.fields.indexOf(field)
-
-  override lazy val resolved = childrenResolved && fieldResolved
-
-  /** Returns true only if the fieldName is found in the child struct. */
-  private def fieldResolved = child.dataType match {
-    case StructType(fields) => fields.map(_.name).contains(fieldName)
-    case _ => false
-  }
-
   override def eval(input: Row): Any = {
     val baseValue = child.eval(input).asInstanceOf[Row]
     if (baseValue == null) null else baseValue(ordinal)
   }
 
-  override def toString = s"$child.$fieldName"
+  override def toString = s"$child.${field.name}"
 }
 
 /**

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

@@ -206,7 +206,7 @@ object NullPropagation extends Rule[LogicalPlan] {
       case e @ IsNotNull(c) if !c.nullable => Literal(true, BooleanType)
       case e @ GetItem(Literal(null, _), _) => Literal(null, e.dataType)
       case e @ GetItem(_, Literal(null, _)) => Literal(null, e.dataType)
-      case e @ GetField(Literal(null, _), _) => Literal(null, e.dataType)
+      case e @ GetField(Literal(null, _), _, _) => Literal(null, e.dataType)
       case e @ EqualNullSafe(Literal(null, _), r) => IsNull(r)
       case e @ EqualNullSafe(l, Literal(null, _)) => IsNull(l)
       case e @ Count(expr) if !expr.nullable => Count(Literal(1))

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala

@@ -18,7 +18,7 @@
 package org.apache.spark.sql.catalyst.plans.logical
 
 import org.apache.spark.Logging
-import org.apache.spark.sql.catalyst.analysis.Resolver
+import org.apache.spark.sql.catalyst.analysis.{UnresolvedGetField, Resolver}
 import org.apache.spark.sql.catalyst.errors.TreeNodeException
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.QueryPlan
@@ -160,11 +160,7 @@ abstract class LogicalPlan extends QueryPlan[LogicalPlan] with Logging {
 
       // One match, but we also need to extract the requested nested field.
       case Seq((a, nestedFields)) =>
-        val aliased =
-          Alias(
-            resolveNesting(nestedFields, a, resolver),
-            nestedFields.last)() // Preserve the case of the user's field access.
-        Some(aliased)
+        Some(Alias(nestedFields.foldLeft(a: Expression)(UnresolvedGetField), nestedFields.last)())
 
       // No matches.
       case Seq() =>
@@ -177,31 +173,6 @@ abstract class LogicalPlan extends QueryPlan[LogicalPlan] with Logging {
           this, s"Ambiguous references to $name: ${ambiguousReferences.mkString(",")}")
     }
   }
-
-  /**
-   * Given a list of successive nested field accesses, and a based expression, attempt to resolve
-   * the actual field lookups on this expression.
-   */
-  private def resolveNesting(
-      nestedFields: List[String],
-      expression: Expression,
-      resolver: Resolver): Expression = {
-
-    (nestedFields, expression.dataType) match {
-      case (Nil, _) => expression
-      case (requestedField :: rest, StructType(fields)) =>
-        val actualField = fields.filter(f => resolver(f.name, requestedField))
-        if (actualField.length == 0) {
-          sys.error(
-            s"No such struct field $requestedField in ${fields.map(_.name).mkString(", ")}")
-        } else if (actualField.length == 1) {
-          resolveNesting(rest, GetField(expression, actualField(0).name), resolver)
-        } else {
-          sys.error(s"Ambiguous reference to fields ${actualField.mkString(", ")}")
-        }
-      case (_, dt) => sys.error(s"Can't access nested field in type $dt")
-    }
-  }
 }
 
 /**

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ExpressionEvaluationSuite.scala

@@ -26,6 +26,7 @@ import org.scalatest.FunSuite
 import org.scalatest.Matchers._
 
 import org.apache.spark.sql.catalyst.dsl.expressions._
+import org.apache.spark.sql.catalyst.analysis.UnresolvedGetField
 import org.apache.spark.sql.types._
 
 
@@ -846,23 +847,33 @@ class ExpressionEvaluationSuite extends FunSuite {
     checkEvaluation(GetItem(BoundReference(4, typeArray, true),
       Literal(null, IntegerType)), null, row)
 
-    checkEvaluation(GetField(BoundReference(2, typeS, nullable = true), "a"), "aa", row)
-    checkEvaluation(GetField(Literal(null, typeS), "a"), null, row)
+    def quickBuildGetField(expr: Expression, fieldName: String) = {
+      expr.dataType match {
+        case StructType(fields) =>
+          val field = fields.find(_.name == fieldName).get
+          GetField(expr, field, fields.indexOf(field))
+      }
+    }
+
+    def quickResolve(u: UnresolvedGetField) = quickBuildGetField(u.child, u.fieldName)
+
+    checkEvaluation(quickBuildGetField(BoundReference(2, typeS, nullable = true), "a"), "aa", row)
+    checkEvaluation(quickBuildGetField(Literal(null, typeS), "a"), null, row)
 
     val typeS_notNullable = StructType(
       StructField("a", StringType, nullable = false)
         :: StructField("b", StringType, nullable = false) :: Nil
     )
 
-    assert(GetField(BoundReference(2,typeS, nullable = true), "a").nullable === true)
-    assert(GetField(BoundReference(2, typeS_notNullable, nullable = false), "a").nullable === false)
+    assert(quickBuildGetField(BoundReference(2,typeS, nullable = true), "a").nullable === true)
+    assert(quickBuildGetField(BoundReference(2, typeS_notNullable, nullable = false), "a").nullable === false)
 
-    assert(GetField(Literal(null, typeS), "a").nullable === true)
-    assert(GetField(Literal(null, typeS_notNullable), "a").nullable === true)
+    assert(quickBuildGetField(Literal(null, typeS), "a").nullable === true)
+    assert(quickBuildGetField(Literal(null, typeS_notNullable), "a").nullable === true)
 
     checkEvaluation('c.map(typeMap).at(3).getItem("aa"), "bb", row)
     checkEvaluation('c.array(typeArray.elementType).at(4).getItem(1), "bb", row)
-    checkEvaluation('c.struct(typeS).at(2).getField("a"), "aa", row)
+    checkEvaluation(quickResolve('c.struct(typeS).at(2).getField("a")), "aa", row)
   }
 
   test("arithmetic") {

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

@@ -17,7 +17,7 @@
 
 package org.apache.spark.sql.catalyst.optimizer
 
-import org.apache.spark.sql.catalyst.analysis.EliminateAnalysisOperators
+import org.apache.spark.sql.catalyst.analysis.{UnresolvedGetField, EliminateAnalysisOperators}
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.logical.{LocalRelation, LogicalPlan}
 import org.apache.spark.sql.catalyst.plans.PlanTest
@@ -184,7 +184,7 @@ class ConstantFoldingSuite extends PlanTest {
 
           GetItem(Literal(null, ArrayType(IntegerType)), 1) as 'c3,
           GetItem(Literal(Seq(1), ArrayType(IntegerType)), Literal(null, IntegerType)) as 'c4,
-          GetField(
+          UnresolvedGetField(
             Literal(null, StructType(Seq(StructField("a", IntegerType, true)))),
             "a") as 'c5,
 

sql/core/src/main/scala/org/apache/spark/sql/Column.scala

@@ -23,6 +23,7 @@ import scala.language.implicitConversions
 import org.apache.spark.sql.Dsl.lit
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.logical.{Subquery, Project, LogicalPlan}
+import org.apache.spark.sql.catalyst.analysis.UnresolvedGetField
 import org.apache.spark.sql.types._
 
 
@@ -505,7 +506,7 @@ trait Column extends DataFrame {
   /**
    * An expression that gets a field by name in a [[StructField]].
    */
-  def getField(fieldName: String): Column = exprToColumn(GetField(expr, fieldName))
+  def getField(fieldName: String): Column = exprToColumn(UnresolvedGetField(expr, fieldName))
 
   /**
    * An expression that returns a substring.