[SPARK-26402][SQL] Accessing nested fields with different cases in case insensitive mode

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

@@ -26,6 +26,7 @@ package org.apache.spark.sql.catalyst.expressions
  *
  * The following rules are applied:
  *  - Names and nullability hints for [[org.apache.spark.sql.types.DataType]]s are stripped.
+ *  - Names for [[GetStructField]] are stripped.
  *  - Commutative and associative operations ([[Add]] and [[Multiply]]) have their children ordered
  *    by `hashCode`.
  *  - [[EqualTo]] and [[EqualNullSafe]] are reordered by `hashCode`.
@@ -37,10 +38,11 @@ object Canonicalize {
     expressionReorder(ignoreNamesTypes(e))
   }
 
-  /** Remove names and nullability from types. */
+  /** Remove names and nullability from types, and names from `GetStructField`. */
   private[expressions] def ignoreNamesTypes(e: Expression): Expression = e match {
     case a: AttributeReference =>
       AttributeReference("none", a.dataType.asNullable)(exprId = a.exprId)
+    case GetStructField(child, ordinal, Some(_)) => GetStructField(child, ordinal, None)
     case _ => e
   }
 

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

@@ -20,6 +20,7 @@ package org.apache.spark.sql.catalyst.expressions
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.sql.catalyst.dsl.plans._
 import org.apache.spark.sql.catalyst.plans.logical.Range
+import org.apache.spark.sql.types.{IntegerType, StructField, StructType}
 
 class CanonicalizeSuite extends SparkFunSuite {
 
@@ -50,4 +51,32 @@ class CanonicalizeSuite extends SparkFunSuite {
     assert(range.where(arrays1).sameResult(range.where(arrays2)))
     assert(!range.where(arrays1).sameResult(range.where(arrays3)))
   }
+
+  test("SPARK-26402: accessing nested fields with different cases in case insensitive mode") {
+    val expId = NamedExpression.newExprId
+    val qualifier = Seq.empty[String]
+    val structType = StructType(
+      StructField("a", StructType(StructField("b", IntegerType, false) :: Nil), false) :: Nil)
+
+    // GetStructField with different names are semantically equal
+    val fieldB1 = GetStructField(
+      AttributeReference("data1", structType, false)(expId, qualifier),
+      0, Some("b1"))
+    val fieldB2 = GetStructField(
+      AttributeReference("data2", structType, false)(expId, qualifier),
+      0, Some("b2"))
+    assert(fieldB1.semanticEquals(fieldB2))
+
+    val fieldA1 = GetStructField(
+      GetStructField(
+        AttributeReference("data1", structType, false)(expId, qualifier),
+        0, Some("a1")),
+      0, Some("b1"))
+    val fieldA2 = GetStructField(
+      GetStructField(
+        AttributeReference("data2", structType, false)(expId, qualifier),
+        0, Some("a2")),
+      0, Some("b2"))
+    assert(fieldA1.semanticEquals(fieldA2))
+  }
 }

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

@@ -25,6 +25,7 @@ import org.apache.spark.sql.catalyst.expressions.Literal.{FalseLiteral, TrueLite
 import org.apache.spark.sql.catalyst.plans.PlanTest
 import org.apache.spark.sql.catalyst.plans.logical._
 import org.apache.spark.sql.catalyst.rules._
+import org.apache.spark.sql.types.{IntegerType, StructField, StructType}
 
 class BinaryComparisonSimplificationSuite extends PlanTest with PredicateHelper {
 
@@ -92,4 +93,33 @@ class BinaryComparisonSimplificationSuite extends PlanTest with PredicateHelper
     val correctAnswer = nonNullableRelation.analyze
     comparePlans(actual, correctAnswer)
   }
+
+  test("SPARK-26402: accessing nested fields with different cases in case insensitive mode") {
+    val expId = NamedExpression.newExprId
+    val qualifier = Seq.empty[String]
+    val structType = StructType(
+      StructField("a", StructType(StructField("b", IntegerType, false) :: Nil), false) :: Nil)
+
+    val fieldA1 = GetStructField(
+      GetStructField(
+        AttributeReference("data1", structType, false)(expId, qualifier),
+        0, Some("a1")),
+      0, Some("b1"))
+    val fieldA2 = GetStructField(
+      GetStructField(
+        AttributeReference("data2", structType, false)(expId, qualifier),
+        0, Some("a2")),
+      0, Some("b2"))
+
+    // GetStructField with different names are semantically equal; thus, `EqualTo(fieldA1, fieldA2)`
+    // will be optimized to `TrueLiteral` by `SimplifyBinaryComparison`.
+    val originalQuery = nonNullableRelation
+        .where(EqualTo(fieldA1, fieldA2))
+        .analyze
+
+    val optimized = Optimize.execute(originalQuery)
+    val correctAnswer = nonNullableRelation.analyze
+
+    comparePlans(optimized, correctAnswer)
+  }
 }

sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala

@@ -2937,6 +2937,25 @@ class SQLQuerySuite extends QueryTest with SharedSQLContext {
       }
     }
   }
+
+  test("SPARK-26402: accessing nested fields with different cases in case insensitive mode") {
+    withSQLConf(SQLConf.CASE_SENSITIVE.key -> "true") {
+      val msg = intercept[AnalysisException] {
+        withTable("t") {
+          sql("create table t (s struct<i: Int>) using json")
+          checkAnswer(sql("select s.I from t group by s.i"), Nil)
+        }
+      }.message
+      assert(msg.contains("No such struct field I in i"))
+    }
+
+    withSQLConf(SQLConf.CASE_SENSITIVE.key -> "false") {
+      withTable("t") {
+        sql("create table t (s struct<i: Int>) using json")
+        checkAnswer(sql("select s.I from t group by s.i"), Nil)
+      }
+    }
+  }
 }
 
 case class Foo(bar: Option[String])