Support Percona-style migration to add a column

Author: nielsreijers

mysql_ch_replicator/converter.py

@@ -354,6 +354,24 @@ def __basic_validate_query(self, mysql_query):
         if mysql_query.find(';') != -1:
             raise Exception('multi-query statement not supported')
         return mysql_query
+    
+    def get_db_and_table_name(self, token, db_name):
+        if '.' in token:
+            db_name, table_name = token.split('.')
+        else:
+            table_name = token
+        db_name = strip_sql_name(db_name)
+        table_name = strip_sql_name(table_name)
+        if self.db_replicator:
+            if db_name == self.db_replicator.database:
+                db_name = self.db_replicator.target_database
+            matches_config = (
+                self.db_replicator.config.is_database_matches(db_name)
+                and self.db_replicator.config.is_table_matches(table_name))
+        else:
+            matches_config = True
+
+        return db_name, table_name, matches_config
 
     def convert_alter_query(self, mysql_query, db_name):
         mysql_query = self.__basic_validate_query(mysql_query)
@@ -365,21 +383,10 @@ def convert_alter_query(self, mysql_query, db_name):
         if tokens[1].lower() != 'table':
             raise Exception('wrong query')
 
-        table_name = tokens[2]
-        if table_name.find('.') != -1:
-            db_name, table_name = table_name.split('.')
+        db_name, table_name, matches_config = self.get_db_and_table_name(tokens[2], db_name)
 
-        if self.db_replicator:
-            if not self.db_replicator.config.is_database_matches(db_name):
-                return
-            if not self.db_replicator.config.is_table_matches(table_name):
-                return
-
-        db_name = strip_sql_name(db_name)
-        if self.db_replicator and db_name == self.db_replicator.database:
-            db_name = self.db_replicator.target_database
-
-        table_name = strip_sql_name(table_name)
+        if not matches_config:
+            return
 
         subqueries = ' '.join(tokens[3:])
         subqueries = split_high_level(subqueries, ',')

mysql_ch_replicator/db_replicator.py

@@ -476,15 +476,17 @@ def handle_query_event(self, event: LogEvent):
         if self.config.debug_log_level:
             logger.debug(f'processing query event: {event.transaction_id}, query: {event.records}')
         query = strip_sql_comments(event.records)
+        self.upload_records()
         if query.lower().startswith('alter'):
             self.handle_alter_query(query, event.db_name)
         if query.lower().startswith('create table'):
             self.handle_create_table_query(query, event.db_name)
         if query.lower().startswith('drop table'):
             self.handle_drop_table_query(query, event.db_name)
+        if query.lower().startswith('rename table'):
+            self.handle_rename_table_query(query, event.db_name)
 
     def handle_alter_query(self, query, db_name):
-        self.upload_records()
         self.converter.convert_alter_query(query, db_name)
 
     def handle_create_table_query(self, query, db_name):
@@ -509,17 +511,41 @@ def handle_drop_table_query(self, query, db_name):
         if len(tokens) != 3:
             raise Exception('wrong token count', query)
 
-        table_name = tokens[2]
-        if '.' in table_name:
-            db_name, table_name = table_name.split('.')
-            if db_name == self.database:
-                db_name = self.target_database
-        table_name = strip_sql_name(table_name)
-        db_name = strip_sql_name(db_name)
+        db_name, table_name, matches_config = self.converter.get_db_and_table_name(tokens[2], db_name)
+        if not matches_config:
+            return
+
         if table_name in self.state.tables_structure:
             self.state.tables_structure.pop(table_name)
         self.clickhouse_api.execute_command(f'DROP TABLE {"IF EXISTS" if if_exists else ""} {db_name}.{table_name}')
 
+    def handle_rename_table_query(self, query, db_name):
+        tokens = query.split()
+        if tokens[0].lower() != 'rename' or tokens[1].lower() != 'table':
+            raise Exception('wrong rename table query', query)
+
+        ch_clauses = []
+        for rename_clause in ' '.join(tokens[2:]).split(','):
+            tokens = rename_clause.split()
+
+            if len(tokens) != 3:
+                raise Exception('wrong token count', query)
+            if tokens[1].lower() != 'to':
+                raise Exception('"to" keyword expected', query)
+
+            src_db_name, src_table_name, matches_config = self.converter.get_db_and_table_name(tokens[0], db_name)
+            dest_db_name, dest_table_name, _ = self.converter.get_db_and_table_name(tokens[2], db_name)
+            if not matches_config:
+                return
+
+            if src_db_name != self.target_database or dest_db_name != self.target_database:
+                raise Exception('cross databases table renames not implemented', tokens)
+            if src_table_name in self.state.tables_structure:
+                self.state.tables_structure[dest_table_name] = self.state.tables_structure.pop(src_table_name)
+
+            ch_clauses.append(f"{src_db_name}.{src_table_name} TO {dest_db_name}.{dest_table_name}")
+        self.clickhouse_api.execute_command(f'RENAME TABLE {", ".join(ch_clauses)}')
+
     def log_stats_if_required(self):
         curr_time = time.time()
         if curr_time - self.last_dump_stats_time < DbReplicator.STATS_DUMP_INTERVAL:

test_mysql_ch_replicator.py

@@ -1098,6 +1098,81 @@ def test_if_exists_if_not_exists(monkeypatch):
     binlog_replicator_runner.stop()
 
 
+def test_percona_migration(monkeypatch):
+    monkeypatch.setattr(DbReplicator, 'INITIAL_REPLICATION_BATCH_SIZE', 1)
+
+    cfg = config.Settings()
+    cfg.load(CONFIG_FILE)
+
+    mysql = mysql_api.MySQLApi(
+        database=None,
+        mysql_settings=cfg.mysql,
+    )
+
+    ch = clickhouse_api.ClickhouseApi(
+        database=TEST_DB_NAME,
+        clickhouse_settings=cfg.clickhouse,
+    )
+
+    prepare_env(cfg, mysql, ch)
+
+    mysql.execute(f'''
+CREATE TABLE {TEST_TABLE_NAME} (
+  `id` int NOT NULL,
+  PRIMARY KEY (`id`)); 
+    ''')
+
+    mysql.execute(
+        f"INSERT INTO {TEST_TABLE_NAME} (id) VALUES (42)",
+        commit=True,
+    )
+
+    binlog_replicator_runner = BinlogReplicatorRunner()
+    binlog_replicator_runner.run()
+    db_replicator_runner = DbReplicatorRunner(TEST_DB_NAME)
+    db_replicator_runner.run()
+
+    assert_wait(lambda: TEST_DB_NAME in ch.get_databases())
+
+    ch.execute_command(f'USE {TEST_DB_NAME}')
+
+    assert_wait(lambda: TEST_TABLE_NAME in ch.get_tables())
+    assert_wait(lambda: len(ch.select(TEST_TABLE_NAME)) == 1)
+
+   # Perform 'pt-online-schema-change' style migration to add a column
+   # This is a subset of what happens when the following command is run:
+   #     pt-online-schema-change --alter "ADD COLUMN c1 INT" D=$TEST_DB_NAME,t=$TEST_TABLE_NAME,h=0.0.0.0,P=3306,u=root,p=admin --execute
+    mysql.execute(f'''
+CREATE TABLE `{TEST_DB_NAME}`.`_{TEST_TABLE_NAME}_new` (
+  `id` int NOT NULL,
+  PRIMARY KEY (`id`)
+)''')
+
+    mysql.execute(
+        f"ALTER TABLE `{TEST_DB_NAME}`.`_{TEST_TABLE_NAME}_new` ADD COLUMN c1 INT;")
+
+    mysql.execute(
+        f"INSERT LOW_PRIORITY IGNORE INTO `{TEST_DB_NAME}`.`_{TEST_TABLE_NAME}_new` (`id`) SELECT `id` FROM `{TEST_DB_NAME}`.`{TEST_TABLE_NAME}` LOCK IN SHARE MODE;",
+        commit=True,
+    )
+
+    mysql.execute(
+        f"RENAME TABLE `{TEST_DB_NAME}`.`{TEST_TABLE_NAME}` TO `{TEST_DB_NAME}`.`_{TEST_TABLE_NAME}_old`, `{TEST_DB_NAME}`.`_{TEST_TABLE_NAME}_new` TO `{TEST_DB_NAME}`.`{TEST_TABLE_NAME}`;")
+
+    mysql.execute(
+        f"DROP TABLE IF EXISTS `{TEST_DB_NAME}`.`_{TEST_TABLE_NAME}_old`;")
+
+    mysql.execute(
+        f"INSERT INTO {TEST_TABLE_NAME} (id, c1) VALUES (43, 1)",
+        commit=True,
+    )
+
+    assert_wait(lambda: len(ch.select(TEST_TABLE_NAME)) == 2)
+
+    db_replicator_runner.stop()
+    binlog_replicator_runner.stop()
+
+
 def test_parse_mysql_table_structure():
     query = "CREATE TABLE IF NOT EXISTS user_preferences_portal (\n\t\t\tid char(36) NOT NULL,\n\t\t\tcategory varchar(50) DEFAULT NULL,\n\t\t\tdeleted tinyint(1) DEFAULT 0,\n\t\t\tdate_entered datetime DEFAULT NULL,\n\t\t\tdate_modified datetime DEFAULT NULL,\n\t\t\tassigned_user_id char(36) DEFAULT NULL,\n\t\t\tcontents longtext DEFAULT NULL\n\t\t ) ENGINE=InnoDB DEFAULT CHARSET=utf8"