Akanksha-kedia opened a new pull request, #18514:
URL: https://github.com/apache/pinot/pull/18514
## Description
Adds a new `broadcast_right` join strategy hint for the multi-stage query
engine. This strategy explicitly broadcasts the right side of a join to all
workers while hash-distributing (or random-distributing for non-equi joins) the
left side. It is designed for star-schema patterns where the right (dimension)
table is small enough to fit in memory but is **not** pre-replicated as a
dimension table — filling the gap between the existing `hash` and `lookup`
strategies.
## Related Issue
Partially addresses #14518 (item 2: "Broadcast the right table, and join on
left table local worker")
## Changes Made
- **`PinotHintOptions.java`** — Added `BROADCAST_RIGHT_JOIN_STRATEGY`
constant and `useBroadcastRightJoinStrategy()` helper method.
- **`PinotJoinExchangeNodeInsertRule.java`** — Handle the new hint in the
exchange-insertion rule: left side gets hash (or random for non-equi)
distribution, right side gets broadcast distribution.
- **`TraitAssignment.java`** — Assign correct distribution traits when
`broadcast_right` hint is present (parallel to existing lookup join handling).
- **`RelToPlanNodeConverter.java`** — Map the hint to
`JoinNode.JoinStrategy.BROADCAST_RIGHT` in the v1 logical-to-physical converter.
- **`PRelToPlanNodeConverter.java`** — Map the hint to
`JoinNode.JoinStrategy.BROADCAST_RIGHT` in the v2 physical planner converter.
- **`JoinNode.java`** — Added `BROADCAST_RIGHT` to the `JoinStrategy` enum.
- **`QueryCompilationTest.java`** — Added two tests covering equi-join (hash
left + broadcast right) and non-equi-join (random left + broadcast right)
scenarios.
## Usage
```sql
SELECT /*+ joinOptions(join_strategy='broadcast_right') */
f.order_id, d.product_name
FROM fact_orders f
JOIN dim_products d ON f.product_id = d.product_id
```
## Testing Done
- [x] Unit tests added (`testBroadcastRightJoinHintEquiJoin`,
`testBroadcastRightJoinHintNonEquiJoin`)
- [x] Tests verify both distribution types (HASH/RANDOM for left, BROADCAST
for right) and the `BROADCAST_RIGHT` join strategy in the plan node
- [x] Existing tests pass — the change is purely additive and does not
modify any existing code paths
## Documentation
- [ ] Documentation update can follow in a separate PR once the strategy is
finalized
## Checklist
- [x] Code follows project style guidelines
- [x] Self-review completed
- [x] No new warnings introduced
- [x] Backward compatible — new enum value is additive; no existing behavior
changed
- [x] Works with both v1 (`RelToPlanNodeConverter`) and v2
(`PRelToPlanNodeConverter`) physical planners
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