[core] Fix push down limit data correctness issue with deletion vector (

#4296)

paimon-core/src/main/java/org/apache/paimon/table/source/DataTableBatchScan.java

@@ -28,6 +28,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 import static org.apache.paimon.CoreOptions.MergeEngine.FIRST_ROW;
 
@@ -114,10 +115,14 @@ private StartingScanner.Result applyPushDownLimit(StartingScanner.Result result)
     }
 
     /**
-     * 0 represents that we can't compute the row count of this split, 'cause this split needs to be
-     * merged.
+     * 0 represents that we can't compute the row count of this split: 1. the split needs to be
+     * merged; 2. the table enabled deletion vector and there are some deletion files.
      */
     private long getRowCountForSplit(DataSplit split) {
+        if (split.deletionFiles().isPresent()
+                && split.deletionFiles().get().stream().anyMatch(Objects::nonNull)) {
+            return 0L;
+        }
         return split.convertToRawFiles()
                 .map(files -> files.stream().map(RawFile::rowCount).reduce(Long::sum).orElse(0L))
                 .orElse(0L);

paimon-spark/paimon-spark-common/src/test/scala/org/apache/paimon/spark/sql/PaimonPushDownTest.scala

@@ -86,6 +86,22 @@ class PaimonPushDownTest extends PaimonSparkTestBase {
     checkAnswer(spark.sql(q), Row(1, "a", "p1") :: Row(2, "b", "p1") :: Row(3, "c", "p2") :: Nil)
   }
 
+  test("Paimon pushDown: limit for append-only tables with deletion vector") {
+    withTable("dv_test") {
+      spark.sql(
+        """
+          |CREATE TABLE dv_test (c1 INT, c2 STRING)
+          |TBLPROPERTIES ('deletion-vectors.enabled' = 'true', 'source.split.target-size' = '1')
+          |""".stripMargin)
+
+      spark.sql("insert into table dv_test values(1, 'a'),(2, 'b'),(3, 'c')")
+      assert(spark.sql("select * from dv_test limit 2").count() == 2)
+
+      spark.sql("delete from dv_test where c1 = 1")
+      assert(spark.sql("select * from dv_test limit 2").count() == 2)
+    }
+  }
+
   test("Paimon pushDown: limit for append-only tables") {
     spark.sql(s"""
                  |CREATE TABLE T (a INT, b STRING, c STRING)