开发组成员们，你们好。 在研究本项目的时候产生了一个疑问，希望能得到解答。 背景：在Galaxy生成的Clichouse DDL中，为每个表建立了”ck_is_delete“列，复制表的引擎选用：ReplicatedMergeTree。 问题：这里为什么没有选用ReplicatedCollapsingMergeTree作为复制表的引擎，使用”sign“代替”ck_is_delete“？

望解答

mongodb test_mongo.example inserted 10000 lines Traceback (most recent call last): File "/tmp/init_db.py", line 74, in init_mongo() File "/tmp/init_db.py", line 69, in init_mongo collection.insert_many(result) File "/usr/local/lib/python3.10/site-packages/pymongo/collection.py", line 615, in insert_many blk.execute(write_concern, session=session) File "/usr/local/lib/python3.10/site-packages/pymongo/bulk.py", line 459, in execute return self.execute_command(generator, write_concern, session) File "/usr/local/lib/python3.10/site-packages/pymongo/bulk.py", line 351, in execute_command with client._tmp_session(session) as s: File "/usr/local/lib/python3.10/contextlib.py", line 135, in enter return next(self.gen) File "/usr/local/lib/python3.10/site-packages/pymongo/mongo_client.py", line 1656, in _tmp_session s = self._ensure_session(session) File "/usr/local/lib/python3.10/site-packages/pymongo/mongo_client.py", line 1643, in _ensure_session return self.__start_session(True, causal_consistency=False) File "/usr/local/lib/python3.10/site-packages/pymongo/mongo_client.py", line 1594, in __start_session server_session = self._get_server_session() File "/usr/local/lib/python3.10/site-packages/pymongo/mongo_client.py", line 1629, in _get_server_session return self._topology.get_server_session() File "/usr/local/lib/python3.10/site-packages/pymongo/topology.py", line 534, in get_server_session session_timeout = self._check_session_support() File "/usr/local/lib/python3.10/site-packages/pymongo/topology.py", line 520, in _check_session_support self._select_servers_loop( File "/usr/local/lib/python3.10/site-packages/pymongo/topology.py", line 223, in _select_servers_loop raise ServerSelectionTimeoutError( pymongo.errors.ServerSelectionTimeoutError: mongo1:30001: [Errno -2] Name or service not known,mongo2:30002: [Errno -2] Name or service not known,mongo3:30003: [Errno -2] Name or service not known, Timeout: 30s, Topology Description: <TopologyDescription id: 624a83e9fd437d56bbaaf7a3, topology_type: ReplicaSetNoPrimary, servers: [<ServerDescription ('mongo1', 30001) server_type: Unknown, rtt: None, error=AutoReconnect('mongo1:30001: [Errno -2] Name or service not known')>, <ServerDescription ('mongo2', 30002) server_type: Unknown, rtt: None, error=AutoReconnect('mongo2:30002: [Errno -2] Name or service not known')>, <ServerDescription ('mongo3', 30003) server_type: Unknown, rtt: None, error=AutoReconnect('mongo3:30003: [Errno -2] Name or service not known')>]> make: *** [init] Error 1

Traceback (most recent call last): File "/tmp/init_db.py", line 74, in init_mongo() File "/tmp/init_db.py", line 69, in init_mongo collection.insert_many(result) File "/usr/local/lib/python3.9/site-packages/pymongo/collection.py", line 761, in insert_many blk.execute(write_concern, session=session) File "/usr/local/lib/python3.9/site-packages/pymongo/bulk.py", line 528, in execute return self.execute_command(generator, write_concern, session) File "/usr/local/lib/python3.9/site-packages/pymongo/bulk.py", line 359, in execute_command client._retry_with_session( File "/usr/local/lib/python3.9/site-packages/pymongo/mongo_client.py", line 1384, in _retry_with_session return self._retry_internal(retryable, func, session, bulk) File "/usr/local/lib/python3.9/site-packages/pymongo/mongo_client.py", line 1414, in _retry_internal raise last_error File "/usr/local/lib/python3.9/site-packages/pymongo/mongo_client.py", line 1416, in _retry_internal return func(session, sock_info, retryable) File "/usr/local/lib/python3.9/site-packages/pymongo/bulk.py", line 353, in retryable_bulk self._execute_command( File "/usr/local/lib/python3.9/site-packages/pymongo/bulk.py", line 309, in _execute_command result, to_send = bwc.execute(ops, client) File "/usr/local/lib/python3.9/site-packages/pymongo/message.py", line 907, in execute result = self.write_command(request_id, msg, to_send) File "/usr/local/lib/python3.9/site-packages/pymongo/message.py", line 999, in write_command reply = self.sock_info.write_command(request_id, msg) File "/usr/local/lib/python3.9/site-packages/pymongo/pool.py", line 771, in write_command helpers._check_command_response(result, self.max_wire_version) File "/usr/local/lib/python3.9/site-packages/pymongo/helpers.py", line 151, in _check_command_response raise NotMasterError(errmsg, response) pymongo.errors.NotMasterError: operation was interrupted, full error: {'errorLabels': ['RetryableWriteError'], 'topologyVersion': {'processId': ObjectId('6071d9eecc09c5721c8f196f'), 'counter': 6}, 'operationTime': Timestamp(1618074848, 500), 'ok': 0.0, 'errmsg': 'operation was interrupted', 'code': 11602, 'codeName': 'InterruptedDueToReplStateChange', '$clusterTime': {'clusterTime': Timestamp(1618074848, 500), 'signature': {'hash': b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00', 'keyId': 0}}} make: *** [init] Error 1

在同步mysql数据时候，发现当字段可以为Null，并且数据是Null的时候，dm 数据同步报nil异常的异常

{"@timestamp":"2021-01-04T17:03:44.268+08","level":"error","content":"mysqltypeconv.go:59 sql: Scan error on column index 4, name "Default": converting NULL to string is unsupported"}

通过如下代码可以解决

环境: centos 7 | clickhouse ClickHouse server version 20.12.5 | cds 最新版(建议添加一个版本号, commitid: 28c51c5)

现像: 在配置好全量同步,执行同步过程出现如下错误:

{"@timestamp":"2021-01-04T17:03:44.268+08","level":"error","content":"mysqltypeconv.go:59 sql: Scan error on column index 4, name \"Default\":
 converting NULL to string is unsupported"}

可能原因: 建表语句指定了字段类型, 导致NULL转换失败

问题:

* 建表语句是否可支持 Nullable
* 全库同步需要选中所有表 ?