BUG23567724: Fix operator names

The operator names were transformed to upper case before being sent to
the server. But the X Plugin expects the operator names to be in lower
case.

With this patch, the Expression Parser converts all operator names to
lower case.

Tests added for regression.

Author: amitab

lib/mysqlx/expr.py

@@ -256,7 +256,7 @@ def lex_alpha(self, i):
             i = i + 1
         val = self.string[start:i]
         try:
-            token = Token(reservedWords[val.lower()], val.upper(), len(val))
+            token = Token(reservedWords[val.lower()], val.lower(), len(val))
         except KeyError:
             token = Token(TokenType.IDENT, val, len(val))
         return token

tests/test_mysqlx_crud.py

@@ -490,6 +490,11 @@ def test_find(self):
         self.assertEqual(42, docs[1]["age"])
         self.assertEqual(1, len(docs[1].keys()))
 
+        # test like operator
+        result = collection.find("$.name like 'B%'").execute()
+        docs = result.fetch_all()
+        self.assertEqual(2, len(docs))
+
         self.schema.drop_collection(collection_name)
 
     def test_modify(self):
@@ -723,6 +728,11 @@ def test_select(self):
         rows = result.fetch_all()
         self.assertEqual(4, len(rows))
 
+        # test like operator
+        result = table.select().where("name like 'B%'").execute()
+        rows = result.fetch_all()
+        self.assertEqual(2, len(rows))
+
         self.schema.drop_table("test")
 
     def test_having(self):