Fix limit pushdown bug when reverse comes before head

Author: Selina Song

opensearch/src/main/java/org/opensearch/sql/opensearch/planner/physical/OpenSearchLimitIndexScanRule.java

@@ -32,6 +32,10 @@ public void onMatch(RelOptRuleCall call) {
 
     Integer limitValue = extractLimitValue(sort.fetch);
     Integer offsetValue = extractOffsetValue(sort.offset);
+    // Skip this rule if this is a reverse operation (indicated by row_number)
+    if (hasRowNumberFunction(sort)) {
+      return;
+    }
     if (limitValue != null && offsetValue != null) {
       CalciteLogicalIndexScan newScan = scan.pushDownLimit(limitValue, offsetValue);
       if (newScan != null) {
@@ -40,6 +44,18 @@ public void onMatch(RelOptRuleCall call) {
     }
   }
 
+  /**
+   * Check if the LogicalSort contains a row_number function, which indicates a reverse operation.
+   *
+   * @param sort The LogicalSort to check
+   * @return True if a row_number function is found, false otherwise
+   */
+  private boolean hasRowNumberFunction(LogicalSort sort) {
+    // Check if the sort has a row_number function in its digest
+    String digest = sort.getDigest();
+    return digest != null && digest.contains("row_number");
+  }
+
   private static Integer extractLimitValue(RexNode fetch) {
     // fetch is always a integer literal (specified in our PPL/SQL syntax)
     if (fetch instanceof RexLiteral) {