[opt](group-commit) Skip createLocation in group commit stream load sink

[liaoxin01]

Summary

The BE-side GroupCommitBlockSinkOperatorX::init does not consume TOlapTableSink.location or slave_location (it only reads tuple_id / schema / db_id / table_id / partition / group_commit_mode / load_id / max_filter_ratio). However, FE still runs createLocation, which iterates O(partitions * indexes * tablets * replicas) and, for every replica, takes the CloudSystemInfoService RW read lock via CloudReplica.getCurrentClusterId.

Under high-concurrency group commit stream load on wide-partition tables (3000+ partitions in a real production incident), CAS contention on the RW lock's state cache line saturated all FE CPUs, and the cluster could not recover even after scaling out (more cores = more CAS contenders = worse contention).

Change

• Introduce a protected initLocationParams(TOlapTableSink) hook on OlapTableSink. Default behavior delegates to createLocation, so non-group-commit sinks are unaffected.
• Route both init(...) overloads in OlapTableSink through the hook.
• GroupCommitBlockSink overrides the hook to return empty placeholder TOlapTableLocationParam objects. TOlapTableSink.location is a required thrift field, so we still set non-null placeholders, but no tablet/replica enumeration happens.

Effect on the group-commit path:

• Per-request FE CPU: O(partitions * indexes * tablets * replicas) → O(1)
• CloudSystemInfoService RW lock acquisitions: hundreds of concurrent CAS spinners → 0

Test plan

• Added GroupCommitBlockSinkTest covering:
  • initLocationParams returns 2 placeholders with empty tablet lists (verifies the override is what runs, not createLocation).
  • parseGroupCommit parses async_mode / sync_mode / off_mode (case-insensitive) and returns null for unknown values.
• Existing regression tests for stream load with group_commit=true still pass.
• Manual high-concurrency stream load run on a wide-partition table to confirm FE CPU is no longer dominated by CloudSystemInfoService lock contention.

[hello-stephen]

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1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
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[liaoxin01]

/review

[liaoxin01]

run buildall

[Copilot]

Pull request overview

Skips the expensive createLocation tablet/replica enumeration for the group-commit stream load sink, which under cloud mode contends on CloudSystemInfoService's RW lock and dominates FE CPU on wide-partition tables. BE's GroupCommitBlockSinkOperatorX::init does not consume location/slave_location, so empty placeholders satisfy the required thrift field at O(1) cost.

Changes:

• Add a protected initLocationParams(TOlapTableSink) hook on OlapTableSink (default delegates to createLocation) and route both init overloads through it.
• Override initLocationParams in GroupCommitBlockSink to return two empty placeholder TOlapTableLocationParam objects.
• Add GroupCommitBlockSinkTest covering the override and parseGroupCommit parsing.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
fe/fe-core/src/main/java/org/apache/doris/planner/OlapTableSink.java	Introduces initLocationParams hook and routes both init overloads through it.
fe/fe-core/src/main/java/org/apache/doris/planner/GroupCommitBlockSink.java	Overrides the hook to return empty placeholder location params, skipping replica enumeration.
fe/fe-core/src/test/java/org/apache/doris/planner/GroupCommitBlockSinkTest.java	New unit tests for the override behavior and parseGroupCommit.

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[github-actions]

Review result: no blocking issues found.

Critical checkpoint conclusions:

• Goal/test coverage: The change avoids FE tablet replica location enumeration for GroupCommitBlockSink while preserving default OlapTableSink behavior. The added unit test covers the override contract and group_commit parsing. I could not run it locally because thirdparty/installed/bin/protoc is absent in this runner, and FE build instructions require stopping before Maven when protoc is missing.
• Scope/focus: The implementation is small and focused: a protected hook plus a GroupCommitBlockSink override.
• Concurrency/locking: The changed FE code does not introduce new shared mutable state or locks. It removes the high-contention createLocation path from the per-request group commit block sink initialization.
• Lifecycle/static initialization: No new lifecycle-sensitive objects or static initialization dependencies were added.
• Configuration/compatibility: No config items or storage/protocol-incompatible fields were added. Required thrift location fields are still populated with non-null placeholders.
• Parallel code paths: Both relevant OlapTableSink init overloads now route through the hook; non-group-commit and RemoteOlapTableSink paths retain createLocation via the default implementation.
• Error handling/data correctness: BE GroupCommitBlockSinkOperatorX::init only consumes schema, partition, ids, group_commit_mode, load_id, and max_filter_ratio; the real internal group-commit insert plan still obtains the normal OLAP sink planning path. I did not find a data visibility or transaction correctness regression from the skipped placeholder locations.
• Observability/performance: The change addresses the intended hot path without adding noisy logs. Existing group commit BE logging remains available.

User focus: No additional user-provided review focus was supplied.

[liaoxin01]

run buildall