Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/5744#discussion_r29315509
--- 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 " +
--- End diff --
one way I can think of to make the error messages more friendly is to
specialize it for each child.datatype.
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