Issue_542: Initialized left node with NullNode instead of null (#564)

* initialized left node with NullNode instead of null and added test for a query starting with NOT statement

* asserted all results rows and removed debug output display

* asserted the size of listOfRaw instead of the whole dataframe

Author: Abigael-JT

src/main/java/com/teragrep/pth10/ast/commands/logicalstatement/LogicalStatementXML.java

@@ -276,8 +276,8 @@ public Node visitDirectoryStatement(DPLParser.DirectoryStatementContext ctx) {
     @Override
     public Node visitLogicalStatement(DPLParser.LogicalStatementContext ctx) {
         LOGGER.info("logicalStatement (XML) incoming: <{}>", ctx.getText());
-        Node rv = null;
-        Node left = null;
+        Node rv = new NullNode();
+        Node left = new NullNode();
         TerminalNode leftIsTerminal = null;
 
         // Visit leftmost child if it is not a terminal node

src/test/java/com/teragrep/pth10/logicalOperationTest.java

@@ -671,4 +671,29 @@ public void testMultipleIndexSourcetypeWithOr() {
             Assertions.assertEquals("\"raw 08\"", listOfRaw.get(3));
         });
     }
+
+    @Test
+    @DisabledIfSystemProperty(
+            named = "skipSparkTest",
+            matches = "true"
+    )
+    public void testNotStatementBeforeIndex() {
+        String query = "NOT (index=index_B OR \"raw 01\")";
+
+        this.streamingTestUtil.performDPLTest(query, this.testFile, res -> {
+            List<String> listOfRaw = res
+                    .select("_raw")
+                    .orderBy("offset")
+                    .collectAsList()
+                    .stream()
+                    .map(r -> r.getAs(0).toString())
+                    .collect(Collectors.toList());
+            Assertions.assertEquals(5, listOfRaw.size()); // 5 rows of data
+            Assertions.assertEquals("\"raw 02\"", listOfRaw.get(0));
+            Assertions.assertEquals("\"raw 03\"", listOfRaw.get(1));
+            Assertions.assertEquals("\"raw 08\"", listOfRaw.get(2));
+            Assertions.assertEquals("\"raw 09\"", listOfRaw.get(3));
+            Assertions.assertEquals("\"raw 10\"", listOfRaw.get(4));
+        });
+    }
 }