[spark] Fix the case that exists filter expression in merge-into on clause (#7334)

Fix this
```sql
MERGE INTO target tgt
USING (
  SELECT a, b
  FROM source
  WHERE c = 'c11'
) AS src
ON tgt.a = src.a AND tgt.b = src.b AND tgt.c = 'cc'
WHEN MATCHED THEN DELETE
```

```
Column '_left.__paimon_file_path' does not exist. Did you mean one of the following? [_left.a, _left.b, _left.c, src.a, src.b]; line 2 pos 0;
'Project ['_left.__paimon_file_path]
+- Join Inner, (((a#56 = a#59) AND (b#57 = b#60)) AND (c#58 = cc))
   :- SubqueryAlias _left
   :  +- Filter (c#58 = cc)
   :     +- SubqueryAlias tgt
   :        +- SubqueryAlias paimon.test.target
   :           +- RelationV2[a#56, b#57, c#58] test.target
   +- SubqueryAlias src
      +- Project [a#59, b#60]
         +- Filter (c#61 = c11)
            +- SubqueryAlias paimon.test.source
               +- RelationV2[a#59, b#60, c#61] test.source
```

Author: Zouxxyy

paimon-spark/paimon-spark-common/src/main/scala/org/apache/paimon/spark/commands/MergeIntoPaimonTable.scala

@@ -142,9 +142,15 @@ case class MergeIntoPaimonTable(
         }
       }
 
+      // If there is filter, we need to output the __paimon__file_path metadata column explicitly.
+      val targetDSWithFilePathCol = targetOnlyCondition.fold(targetDS) {
+        condition =>
+          createDataset(sparkSession, Filter.apply(condition, relation.withMetadataColumns()))
+      }
+
       def findTouchedFiles0(joinType: String): Array[String] = {
         findTouchedFiles(
-          targetDS.alias("_left").join(sourceDS, toColumn(mergeCondition), joinType),
+          targetDSWithFilePathCol.alias("_left").join(sourceDS, toColumn(mergeCondition), joinType),
           sparkSession,
           "_left." + FILE_PATH_COLUMN)
       }

paimon-spark/paimon-spark-ut/src/test/scala/org/apache/paimon/spark/sql/MergeIntoTableTestBase.scala

@@ -665,6 +665,29 @@ abstract class MergeIntoTableTestBase extends PaimonSparkTestBase with PaimonTab
     }
   }
 
+  test(s"Paimon MergeInto: on clause has filter expression") {
+    withTable("source", "target") {
+      createTable("target", "a INT, b INT, c STRING", Seq("a"))
+      createTable("source", "a INT, b INT, c STRING", Seq("a"))
+
+      sql("INSERT INTO source VALUES (1, 100, 'c11'), (3, 300, 'c11'), (5, 500, 'c55')")
+      sql("INSERT INTO target VALUES (1, 100, 'cc'), (2, 20, 'cc')")
+
+      sql("""
+            |MERGE INTO target tgt
+            |USING (
+            |  SELECT a, b
+            |  FROM source
+            |  WHERE c = 'c11'
+            |) AS src
+            |ON tgt.a = src.a AND tgt.b = src.b AND tgt.c = 'cc'
+            |WHEN MATCHED THEN DELETE
+            |""".stripMargin)
+
+      checkAnswer(sql("SELECT * FROM target ORDER BY a, b"), Row(2, 20, "cc") :: Nil)
+    }
+  }
+
   test(s"Paimon MergeInto: merge into with varchar") {
     withTable("source", "target") {
       createTable("source", "a INT, b VARCHAR(32)", Seq("a"))