CI found one hanged query [1], where the problem was that becase of
allow_experimental_parallel_reading_from_replicas the Cancel packet was
read by receivePartitionMergeTreeReadTaskResponseAssumeLocked() and so
the executor was not cancelled, while the code in
MergeTreeBaseSelectProcessor was not ready for this:
<details>
{
"is_initial_query": 0,
"elapsed": 1727.714379573,
"is_cancelled": 0,
"read_rows": "196577",
"read_bytes": "1179462",
"written_rows": "0",
"written_bytes": "0",
"query": "SELECT `CounterID`, `EventDate` FROM `test`.`hits` ORDER BY `CounterID` DESC, `EventDate` ASC LIMIT 50",
...
}
In logs:
2021.12.31 12:11:55.384735 [ 101532 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Debug> executeQuery: (from [::ffff:127.0.0.1]:58094, initial_query_id: e2966ca5-e836-44ef-8f8e-d1c1b32a>
2021.12.31 12:11:55.454379 [ 101532 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Trace> ContextAccess (default): Access granted: SELECT(EventDate, CounterID) ON test.hits
2021.12.31 12:11:55.457583 [ 101532 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Trace> datasets.hits_v1: Parallel reading from replicas enabled true
2021.12.31 12:11:55.459739 [ 101532 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Trace> InterpreterSelectQuery: FetchColumns -> WithMergeableStateAfterAggregationAndLimit
2021.12.31 12:11:55.471048 [ 101532 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Debug> datasets.hits_v1 (SelectExecutor): Key condition: unknown
2021.12.31 12:11:55.476514 [ 101532 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Debug> datasets.hits_v1 (SelectExecutor): MinMax index condition: unknown
2021.12.31 12:11:55.488302 [ 101532 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Debug> datasets.hits_v1 (SelectExecutor): Selected 2/2 parts by partition key, 2 parts by primary key, >
2021.12.31 12:11:55.494020 [ 101532 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Debug> MergeTreeReverseSelectProcessor: Reading 1 ranges in reverse order from part 201403_20_20_0, app>
2021.12.31 12:11:55.497644 [ 101532 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Debug> MergeTreeReverseSelectProcessor: Reading 138 ranges in reverse order from part 201403_19_19_2, a>
2021.12.31 12:11:55.536372 [ 170601 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Compact part, average mark size is 83886080
2021.12.31 12:11:55.558783 [ 171701 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Wide part, average mark size is 3069
2021.12.31 12:11:55.563960 [ 171701 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Wide part, average mark size is 3069
2021.12.31 12:11:55.577512 [ 171701 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Wide part, average mark size is 3069
2021.12.31 12:11:55.585660 [ 171701 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Wide part, average mark size is 3069
2021.12.31 12:11:55.613694 [ 170601 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Wide part, average mark size is 3069
2021.12.31 12:11:55.730597 [ 170601 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Wide part, average mark size is 3069
2021.12.31 12:11:55.743554 [ 171701 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Debug> MergingSortedTransform: Merge sorted 3 blocks, 65567 rows in 0.243999671 sec., 268717.5754429603>
2021.12.31 12:11:55.744196 [ 170601 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Wide part, average mark size is 3069
2021.12.31 12:11:55.890923 [ 170601 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Wide part, average mark size is 3069
2021.12.31 12:11:55.891222 [ 170601 ] {7e5f551e-5960-4fda-9447-9bfdae4660c1} <Test> MergeTreeBaseSelectProcessor: Reading from Wide part, average mark size is 3069
</details>
[1]: https://s3.amazonaws.com/clickhouse-test-reports/33341/0685fd99855bacd0bce02507c00a3bd7709eea61/stress_test__address__actions_.html
