Fix: Properly escape SQL identifiers to handle reserved keywords like key (#162)

* Fix the conflict issue with reserved keywords.

* Remove the SQL query print statement used for debugging

---------

Co-authored-by: liandong <[email protected]>

Author: liandong00

mysql_ch_replicator/mysql_api.py

@@ -95,26 +95,35 @@ def get_table_create_statement(self, table_name) -> str:
 
     def get_records(self, table_name, order_by, limit, start_value=None, worker_id=None, total_workers=None):
         self.reconnect_if_required()
-        order_by_str = ','.join(order_by)
+
+        # Escape column names with backticks to avoid issues with reserved keywords like "key"
+        order_by_escaped = [f'`{col}`' for col in order_by]
+        order_by_str = ','.join(order_by_escaped)
+
         where = ''
         if start_value is not None:
-            start_value = ','.join(map(str, start_value))
-            where = f'WHERE ({order_by_str}) > ({start_value}) '
+            # Build the start_value condition for pagination
+            start_value_str = ','.join(map(str, start_value))
+            where = f'WHERE ({order_by_str}) > ({start_value_str}) '
 
-        # Add partitioning filter for parallel processing if needed
+        # Add partitioning filter for parallel processing (e.g., sharded crawling)
         if worker_id is not None and total_workers is not None and total_workers > 1:
-            # Use a list comprehension to build the COALESCE expressions with proper quoting
-            coalesce_expressions = [f"COALESCE({key}, '')" for key in order_by]
+            # Escape column names in COALESCE expressions
+            coalesce_expressions = [f"COALESCE(`{key}`, '')" for key in order_by]
             concat_keys = f"CONCAT_WS('|', {', '.join(coalesce_expressions)})"
             hash_condition = f"CRC32({concat_keys}) % {total_workers} = {worker_id}"
+
             if where:
                 where += f'AND {hash_condition} '
             else:
                 where = f'WHERE {hash_condition} '
-        
+
+        # Construct final query
         query = f'SELECT * FROM `{table_name}` {where}ORDER BY {order_by_str} LIMIT {limit}'
 
-        # Execute the actual query
+#         print("Executing query:", query)
+
+        # Execute the query
         self.cursor.execute(query)
         res = self.cursor.fetchall()
         records = [x for x in res]