Verify table structure after initial replication (#142)

Author: bakwc

mysql_ch_replicator/db_replicator_initial.py

@@ -103,6 +103,9 @@ def perform_initial_replication(self):
             start_table = None
 
         if not self.replicator.is_parallel_worker:
+            # Verify table structures after replication but before swapping databases
+            self.verify_table_structures_after_replication()
+            
             logger.info(f'initial replication - swapping database')
             if self.replicator.target_database in self.replicator.clickhouse_api.get_databases():
                 self.replicator.clickhouse_api.execute_command(
@@ -216,6 +219,115 @@ def perform_initial_replication_table(self, table_name):
         )
         self.save_state_if_required(force=True)
 
+    def verify_table_structures_after_replication(self):
+        """
+        Verify that MySQL table structures haven't changed during the initial replication process.
+        This helps ensure data integrity by confirming the source tables are the same as when 
+        replication started.
+        
+        Raises an exception if any table structure has changed, preventing the completion
+        of the initial replication process.
+        """
+        logger.info('Verifying table structures after initial replication')
+        
+        changed_tables = []
+        
+        for table_name in self.replicator.state.tables:
+            if not self.replicator.config.is_table_matches(table_name):
+                continue
+                
+            if self.replicator.single_table and self.replicator.single_table != table_name:
+                continue
+                
+            # Get the current MySQL table structure
+            current_mysql_create_statement = self.replicator.mysql_api.get_table_create_statement(table_name)
+            current_mysql_structure = self.replicator.converter.parse_mysql_table_structure(
+                current_mysql_create_statement, required_table_name=table_name,
+            )
+            
+            # Get the original structure used at the start of replication
+            original_mysql_structure, _ = self.replicator.state.tables_structure.get(table_name, (None, None))
+            
+            if not original_mysql_structure:
+                logger.warning(f'Could not find original structure for table {table_name}')
+                continue
+            
+            # Compare the structures in a deterministic way
+            structures_match = self._compare_table_structures(original_mysql_structure, current_mysql_structure)
+                
+            if not structures_match:
+                logger.warning(
+                    f'\n\n\n    !!!  WARNING - TABLE STRUCTURE CHANGED DURING REPLICATION (table "{table_name}") !!!\n\n'
+                    'The MySQL table structure has changed since the initial replication started.\n'
+                    'This may cause data inconsistency and replication issues.\n'
+                )
+                logger.error(f'Original structure: {original_mysql_structure}')
+                logger.error(f'Current structure: {current_mysql_structure}')
+                changed_tables.append(table_name)
+            else:
+                logger.info(f'Table structure verification passed for {table_name}')
+        
+        # If any tables have changed, raise an exception to abort the replication process
+        if changed_tables:
+            error_message = (
+                f"Table structure changes detected in: {', '.join(changed_tables)}. "
+                "Initial replication aborted to prevent data inconsistency. "
+                "Please restart replication after reviewing the changes."
+            )
+            logger.error(error_message)
+            raise Exception(error_message)
+                
+        logger.info('Table structure verification completed')
+    
+    def _compare_table_structures(self, struct1, struct2):
+        """
+        Compare two TableStructure objects in a deterministic way.
+        Returns True if the structures are equivalent, False otherwise.
+        """
+        # Compare basic attributes
+        if struct1.table_name != struct2.table_name:
+            logger.error(f"Table name mismatch: {struct1.table_name} vs {struct2.table_name}")
+            return False
+            
+        if struct1.charset != struct2.charset:
+            logger.error(f"Charset mismatch: {struct1.charset} vs {struct2.charset}")
+            return False
+            
+        # Compare primary keys (order matters)
+        if len(struct1.primary_keys) != len(struct2.primary_keys):
+            logger.error(f"Primary key count mismatch: {len(struct1.primary_keys)} vs {len(struct2.primary_keys)}")
+            return False
+            
+        for i, key in enumerate(struct1.primary_keys):
+            if key != struct2.primary_keys[i]:
+                logger.error(f"Primary key mismatch at position {i}: {key} vs {struct2.primary_keys[i]}")
+                return False
+                
+        # Compare fields (count and attributes)
+        if len(struct1.fields) != len(struct2.fields):
+            logger.error(f"Field count mismatch: {len(struct1.fields)} vs {len(struct2.fields)}")
+            return False
+            
+        for i, field1 in enumerate(struct1.fields):
+            field2 = struct2.fields[i]
+            
+            if field1.name != field2.name:
+                logger.error(f"Field name mismatch at position {i}: {field1.name} vs {field2.name}")
+                return False
+                
+            if field1.field_type != field2.field_type:
+                logger.error(f"Field type mismatch for {field1.name}: {field1.field_type} vs {field2.field_type}")
+                return False
+                
+            # Compare parameters - normalize whitespace to avoid false positives
+            params1 = ' '.join(field1.parameters.lower().split())
+            params2 = ' '.join(field2.parameters.lower().split())
+            if params1 != params2:
+                logger.error(f"Field parameters mismatch for {field1.name}: {params1} vs {params2}")
+                return False
+                
+        return True
+
     def perform_initial_replication_table_parallel(self, table_name):
         """
         Execute initial replication for a table using multiple parallel worker processes.

mysql_ch_replicator/mysql_api.py

@@ -113,7 +113,6 @@ def get_records(self, table_name, order_by, limit, start_value=None, worker_id=N
                 where = f'WHERE {hash_condition} '
 
         query = f'SELECT * FROM `{table_name}` {where}ORDER BY {order_by_str} LIMIT {limit}'
-        print("query:", query)
 
         # Execute the actual query
         self.cursor.execute(query)