Revert "[SPARK-54595][SQL] Keep existing behavior of MERGE INTO without SCHEMA EVOLUTION clause"

This reverts commit 74b6a93.

Author: dongjoon-hyun

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

@@ -1736,8 +1736,9 @@ class Analyzer(
                     Assignment(key, sourceAttr)
                   }
                 } else {
-                  targetTable.output.map { attr =>
-                    Assignment(attr, UnresolvedAttribute(Seq(attr.name)))
+                  sourceTable.output.flatMap { sourceAttr =>
+                    findAttrInTarget(sourceAttr.name).map(
+                      targetAttr => Assignment(targetAttr, sourceAttr))
                   }
                 }
                 UpdateAction(
@@ -1774,8 +1775,9 @@ class Analyzer(
                     Assignment(key, sourceAttr)
                   }
                 } else {
-                  targetTable.output.map { attr =>
-                    Assignment(attr, UnresolvedAttribute(Seq(attr.name)))
+                  sourceTable.output.flatMap { sourceAttr =>
+                    findAttrInTarget(sourceAttr.name).map(
+                      targetAttr => Assignment(targetAttr, sourceAttr))
                   }
                 }
                 InsertAction(

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

@@ -53,7 +53,7 @@ object ResolveRowLevelCommandAssignments extends Rule[LogicalPlan] {
     case m: MergeIntoTable if !m.skipSchemaResolution && m.resolved && m.rewritable && !m.aligned &&
       !m.needSchemaEvolution =>
       validateStoreAssignmentPolicy()
-      val coerceNestedTypes = SQLConf.get.coerceMergeNestedTypes && m.withSchemaEvolution
+      val coerceNestedTypes = SQLConf.get.coerceMergeNestedTypes
       m.copy(
         targetTable = cleanAttrMetadata(m.targetTable),
         matchedActions = alignActions(m.targetTable.output, m.matchedActions,