system.distributed_ddl_queue parses the queries that it finds in ZK #75011
Description
Company or project name
No response
Describe the unexpected behaviour
When querying system.distributed_ddl_queue ClickHouse tries to parse the DDDL statement and throws errors when it is not possible.
Normally exceptions shouldn't happen as queries are parsed before being submitted into the DDDL queue, but it is still possible.
For example, after a downgrade system.distributed_ddl_queue will be enable to parse queries if they used syntax that was unavailable in older releases.
How to reproduce
In my example here I ran a drop table query and then changed the query manually in ZK.
Now selects from system.distributed_ddl_queue fail.
It is not clear why system.distributed_ddl_queue should parse the queries that it finds in ZK.
SELECT *
FROM system.zookeeper
WHERE path = '/clickhouse/task_queue/ddl/'
Query id: 212cd645-d32e-4d38-8a3a-925e0dcb37db
┌─name────────────────────┬─value────────────────────┬─path─────────────────────────────────────────────────┐
1. │ query-0000000001 │ version: 5
query: drop TABLEa default.qq ON CLUSTER mycluster
hosts: ['ch1%2549:9000']
initiator: ch1%2549:9000
tracing: 00000000-0000-0000-0000-000000000000
0
0
initial_query_id: 58958efa-d685-4221-a311-a93216c358b1 │ /clickhouse/task_queue/ddl/ │
2. │ active │ │ /clickhouse/task_queue/ddl/query-0000000001 │
3. │ finished │ │ /clickhouse/task_queue/ddl/query-0000000001 │
4. │ ch1%2549:9000 │ 0 │ /clickhouse/task_queue/ddl/query-0000000001/finished │
└─────────────────────────┴──────────────────────────┴──────────────────────────────────────────────────────┘
SELECT *
FROM system.distributed_ddl_queue
Query id: 68e977f6-41d5-4c7e-8d94-ad4d9d8f6e6b
Elapsed: 0.002 sec.
Received exception from server (version 24.12.3):
Code: 62. DB::Exception: Received from localhost:9000. DB::Exception: Syntax error (from /clickhouse/task_queue/ddl/query-0000000001): failed at position 6 ('TABLEa'): TABLEa default.qq ON CLUSTER segmented. Expected one of: DATABASE, ALL, VIEW, DICTIONARY, TEMPORARY, TABLE, FUNCTION, WORKLOAD, RESOURCE, NAMED COLLECTION, INDEX, USER, ROLE, SETTINGS PROFILE, PROFILE, ROW POLICY, POLICY, QUOTA. (SYNTAX_ERROR)
Expected behavior
I would expect system.distributed_ddl_queue to display the content of the DDDL queue without trying to interpret it.
Error message and/or stacktrace
No response
Additional context
No response