Squashed commits:

  - 0e54b264f0ad74207f4b47ce9fc79d42698fff81 minor by jackierwzhang <ruowang.zhang@databricks.com>
  - 2378e77c2c5601c549696c169d3f5f82cc942a75 use union by jackierwzhang <ruowang.zhang@databricks.com>
  - bf1c0cfd02fbd68d049985624bb5b098317b76ec fix merge conf by jackierwzhang <ruowang.zhang@databricks.com>
  - a5b353370892c14e4c2da5723fccc41584df4950 Squashed commit of the following: by jackierwzhang <ruowang.zhang@databricks.com>

GitOrigin-RevId: 0e54b264f0ad74207f4b47ce9fc79d42698fff81

Author: jackierwzhang

core/src/main/scala/org/apache/spark/sql/delta/sources/DeltaSource.scala

@@ -218,7 +218,7 @@ trait DeltaSourceBase extends Source
       isStartingVersion: Boolean,
       limits: Option[AdmissionLimits] = Some(new AdmissionLimits())):
   ClosableIterator[IndexedFile] = {
-    var iter = if (options.readChangeFeed) {
+    val iter = if (options.readChangeFeed) {
       // In this CDC use case, we need to consider RemoveFile and AddCDCFiles when getting the
       // offset.
 
@@ -242,8 +242,8 @@ trait DeltaSourceBase extends Source
         }
       }
     }
-    iter = stopIndexedFileIteratorAtSchemaChangeBarrier(iter)
-    iter
+    // Stop before any schema change barrier if detected.
+    stopIndexedFileIteratorAtSchemaChangeBarrier(iter)
   }
 
   /**