Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/5744#discussion_r29308710
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/GetField.scala
---
@@ -0,0 +1,199 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalyst.expressions
+
+import scala.collection.Map
+
+import org.apache.spark.sql.AnalysisException
+import org.apache.spark.sql.catalyst.analysis._
+import org.apache.spark.sql.types._
+
+object GetField {
+ /**
+ * Returns the resolved `GetField`. It will return one kind of concrete
`GetField`,
+ * depend on the type of `child` and `fieldExpr`.
+ */
+ def apply(
+ child: Expression,
+ fieldExpr: Expression,
+ resolver: Resolver): GetField = {
+
+ (child.dataType, fieldExpr) match {
+ case (StructType(fields), Literal(fieldName, StringType)) =>
+ val ordinal = findField(fields, fieldName.toString, resolver)
+ SimpleStructGetField(child, fields(ordinal), ordinal)
+ case (ArrayType(StructType(fields), containsNull),
Literal(fieldName, StringType)) =>
+ val ordinal = findField(fields, fieldName.toString, resolver)
+ ArrayStructGetField(child, fields(ordinal), ordinal, containsNull)
+ case (_: ArrayType, _) if
fieldExpr.dataType.isInstanceOf[IntegralType] =>
+ ArrayOrdinalGetField(child, fieldExpr)
+ case (_: MapType, _) =>
+ MapOrdinalGetField(child, fieldExpr)
+ case (otherType, _) =>
+ throw new AnalysisException(
+ "GetField is not valid on child of type " +
+ s"$otherType with fieldExpr of type ${fieldExpr.dataType}")
+ }
+ }
+
+ def unapply(g: GetField): Option[(Expression, Expression)] = {
+ g match {
+ case _: StructGetField => Some((g.child, null))
+ case o: OrdinalGetField => Some((o.child, o.ordinal))
+ case _ => None
+ }
+ }
+
+ /**
+ * find the ordinal of StructField, report error if no desired field or
over one
+ * desired fields are found.
+ */
+ private def findField(fields: Array[StructField], fieldName: String,
resolver: Resolver): Int = {
+ val checkField = (f: StructField) => resolver(f.name, fieldName)
+ val ordinal = fields.indexWhere(checkField)
+ if (ordinal == -1) {
+ throw new AnalysisException(
+ s"No such struct field $fieldName in
${fields.map(_.name).mkString(", ")}")
+ } else if (fields.indexWhere(checkField, ordinal + 1) != -1) {
+ throw new AnalysisException(
+ s"Ambiguous reference to fields
${fields.filter(checkField).mkString(", ")}")
+ } else {
+ ordinal
+ }
+ }
+}
+
+trait GetField extends UnaryExpression {
+ self: Product =>
+
+ type EvaluatedType = Any
+}
+
+abstract class StructGetField extends GetField {
+ self: Product =>
+
+ def field: StructField
+
+ override def foldable: Boolean = child.foldable
+ override def toString: String = s"$child.${field.name}"
+}
+
+abstract class OrdinalGetField extends GetField {
+ self: Product =>
+
+ def ordinal: Expression
+
+ /** `Null` is returned for invalid ordinals. */
+ override def nullable: Boolean = true
+ override def foldable: Boolean = child.foldable && ordinal.foldable
+ override def toString: String = s"$child[$ordinal]"
+ override def children: Seq[Expression] = child :: ordinal :: Nil
+
+ override def eval(input: Row): Any = {
+ val value = child.eval(input)
+ if (value == null) {
+ null
+ } else {
+ val o = ordinal.eval(input)
+ if (o == null) {
+ null
+ } else {
+ evalNotNull(value, o)
+ }
+ }
+ }
+
+ protected def evalNotNull(value: Any, ordinal: Any): Any
+}
+
+/**
+ * Returns the value of fields in the Struct `child`.
+ */
+case class SimpleStructGetField(child: Expression, field: StructField,
ordinal: Int)
+ extends StructGetField {
+
+ override def dataType: DataType = field.dataType
+ override def nullable: Boolean = child.nullable || field.nullable
+
+ override def eval(input: Row): Any = {
+ val baseValue = child.eval(input).asInstanceOf[Row]
+ if (baseValue == null) null else baseValue(ordinal)
+ }
+}
+
+/**
+ * Returns the array of value of fields in the Array of Struct `child`.
+ */
+case class ArrayStructGetField(
--- End diff --
see https://issues.apache.org/jira/browse/SPARK-2096.
"arrayOfStruct.field1" means to access all values of "field1" in this array
of structs and the returns those values as an array.
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