fixes

Signed-off-by: Kai Huang <[email protected]>

Author: ahkcs

integ-test/src/test/java/org/opensearch/sql/calcite/CalciteNoPushdownIT.java

@@ -88,6 +88,7 @@
   CalciteQueryAnalysisIT.class,
   CalciteRareCommandIT.class,
   CalciteRegexCommandIT.class,
+  CalciteReverseCommandIT.class,
   CalciteRexCommandIT.class,
   CalciteRenameCommandIT.class,
   CalciteReplaceCommandIT.class,

integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalciteExplainIT.java

@@ -411,16 +411,26 @@ public void testFilterWithSearchCall() throws IOException {
 
   @Test
   public void testExplainWithReverse() throws IOException {
-    String result =
-        executeWithReplace(
-            "explain source=opensearch-sql_test_index_account | sort age | reverse | head 5");
+    String query = "source=opensearch-sql_test_index_account | reverse | head 5";
+    var result = explainQueryToString(query);
+    String expected = loadExpectedPlan("explain_reverse_fallback.json");
+    assertJsonEqualsIgnoreId(expected, result);
+  }
 
-    // Verify that the plan contains a LogicalSort with fetch (from head 5)
-    assertTrue(result.contains("LogicalSort") && result.contains("fetch=[5]"));
+  @Test
+  public void testExplainWithReversePushdown() throws IOException {
+    String query = "source=opensearch-sql_test_index_account | sort - age | reverse";
+    var result = explainQueryToString(query);
+    String expected = loadExpectedPlan("explain_reverse_pushdown_single.json");
+    assertJsonEqualsIgnoreId(expected, result);
+  }
 
-    // Verify that reverse added a ROW_NUMBER and another sort (descending)
-    assertTrue(result.contains("ROW_NUMBER()"));
-    assertTrue(result.contains("dir0=[DESC]"));
+  @Test
+  public void testExplainWithReversePushdownMultipleFields() throws IOException {
+    String query = "source=opensearch-sql_test_index_account | sort - age, + firstname | reverse";
+    var result = explainQueryToString(query);
+    String expected = loadExpectedPlan("explain_reverse_pushdown_multiple.json");
+    assertJsonEqualsIgnoreId(expected, result);
   }
 
   @Test