Docs: clarify description of parallel_distributed_insert_select#104607
Conversation
|
Workflow [PR], commit [347af01] Summary: ✅ AI ReviewSummaryThis PR updates the description of Findings❌ Blockers
Final VerdictStatus:
|
clickhouse-gh
Bot
added
the
pr-documentation
![clickhouse-gh[bot]](https://avatars.githubusercontent.com/in/928874?s=60&v=4){kind=small}
| Setting `enable_parallel_replicas = 1` is needed when using this setting. | ||
| Since v25.4, `INSERT ... SELECT` from a `ReplicatedMergeTree` or `SharedMergeTree` source can also be parallelized across replicas. To enable it: | ||
| - `parallel_distributed_insert_select = 2` | ||
| - `enable_parallel_replicas = 1` |
There was a problem hiding this comment.
The "To enable it" prerequisites are still incomplete for OSS users. Setting enable_parallel_replicas = 1 is not sufficient by itself here: this path eventually relies on Context::getClusterForParallelReplicas, and with the default empty cluster_for_parallel_replicas it throws CLUSTER_DOESNT_EXIST.
Could we either list cluster_for_parallel_replicas as an explicit requirement, or scope this sentence to environments where it is preconfigured (for example Cloud)?
There was a problem hiding this comment.
I re-checked this on current master-based code and the requirement is still present for the ReplicatedMergeTree / SharedMergeTree case.
isSuitableForInsertSelectWithParallelReplicas still plans the query via InterpreterSelectQueryAnalyzer, and the parallel-replica path still goes through Context::getClusterForParallelReplicas (see src/Interpreters/ClusterProxy/executeQuery.cpp and src/Interpreters/Context.cpp). With empty cluster_for_parallel_replicas, it throws CLUSTER_DOESNT_EXIST.
So the "To enable it" list is still incomplete for OSS unless it also mentions cluster_for_parallel_replicas (or explicitly scopes the statement to environments where it is preconfigured).
|
This was fixed by #105146. Let's update the branch. |
LLVM Coverage ReportChanged lines: 100.00% (8/8) · Uncovered code |
robot-ch-test-poll4
added
the
pr-synced-to-cloud
4 participants
Clarifies an inaccurate docs description. Description was previously updated to say:
However this is an over-simplification.
Source: https://github.com/ClickHouse/ClickHouse/blob/master/src/Interpreters/ClusterProxy/executeQuery.cpp (
isSuitableForInsertSelectWithParallelReplicasfunction). introduced in #78041.As I see it:
Changelog category (leave one):
Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):
...
Documentation entry for user-facing changes
Version info
26.5.1.773