Add SQL reference page for ALTER PARALLELISM #957
Description
Context
Slack thread: https://slack.com/archives/C034XCYJPSN/p1770678128292929
Problem
Users cannot find documentation for the ALTER ... SET PARALLELISM SQL command in the SQL reference. The feature exists and is referenced in various docs/PRs, but there is no dedicated SQL reference page under sql/commands, creating a gap for syntax, behavior, and usage guidance.
Suggested Fix
- Add a new SQL reference page for
ALTER ... SET PARALLELISMundersql/commandswith syntax, parameters, supported object types, and examples. - Clarify operational notes: impact on running jobs, any limits, and constraints (e.g., max parallelism).
- Add cross-links from related docs (e.g., cluster limits, scaling, and existing alter-* commands) to improve discoverability.
Existing Documentation
- performance/faq.mdx
- operate/cluster-limit.mdx
- reference/key-concepts.mdx
- deploy/k8s-cluster-scaling.mdx
- sql/commands/sql-alter-sink.mdx
- operate/manage-a-large-number-of-streaming-jobs.mdx
Related docs PRs:
Codebase References
Related PRs in risingwave:
- feat: alter parallelism use deferred mode during recovery state
- feat: add reschedule support for backfilling jobs
- feat: support window function in datafusion
- feat(iceberg): improve iceberg decimal handling: adjust ICEBERG_DECIMAL_PRECISION = 38
- fix(optimizer): improve table scan better locality index selection
Source files:
risingwavelabs/risingwave/src/frontend/src/handler/alter_parallelism.rsrisingwavelabs/risingwave/src/meta/src/rpc/ddl_controller.rsrisingwavelabs/risingwave/src/meta/src/manager/sink_coordination/coordinator_worker.rsrisingwavelabs/risingwave/e2e_test/ddl/max_parallelism.sltrisingwavelabs/risingwave/e2e_test/source_inline/kafka/alter/alter_parallelism.slt