Alena0704 opened a new pull request, #1719:
URL: https://github.com/apache/cloudberry/pull/1719
### What does this PR do?
Fixes a query hang in ORCA when a CTE over a replicated table is referenced
from a different executor slice than its Producer (e.g. from a scalar
subquery, or via duplicate-hazard motion in a JOIN).
Before Expr→DXL translation, the patch walks the physical tree and tracks
which slice each CTE Producer and Consumer lives on (slices are delimited
by Motion nodes). If any Consumer is on a different slice than its Producer
*and* the Producer's distribution is replicated-like
(StrictReplicated / TaintedReplicated / Universal), ORCA raises an
unsupported-feature exception and falls back to the Postgres planner.
The replicated filter is essential: ordinary cross-slice CTE plans
(non-replicated Producer with Gather/Redistribute Consumer) are a normal
ORCA pattern and must not trigger fallback.
Inspired by greengage 51fe92e, but extends it: 51fe92e's single-point check
doesn't trigger when a CTE over a replicated table is referenced from a
scalar subquery, so the query hangs. This PR replaces it with a whole-tree
walker that catches both cases.
### Type of Change
- [x] Bug fix (non-breaking change)
- [ ] New feature (non-breaking change)
- [ ] Breaking change (fix or feature with breaking changes)
- [ ] Documentation update
### Breaking Changes
None.
### Test Plan
- [x] Unit tests added/updated
- [x] Integration tests added/updated
- [ ] Passed `make installcheck`
- [ ] Passed `make -C src/test installcheck-cbdb-parallel`
Two regression cases added:
- `qp_orca_fallback`: original 51fe92e reproducer — JOIN over a CTE
referencing replicated tables with duplicate-hazard motion.
- `shared_scan`: scalar-subquery reproducer where a CTE over a replicated
table is referenced from multiple `(SELECT … FROM cte)` expressions.
Guarded by `statement_timeout = '15s'` so the test fails fast if the
hang regresses (40k rows in the driving table are needed to push ORCA
to the cross-slice plan — fewer rows would make the test silently pass
without the fix).
### Impact
**Performance:** Negligible. The added walker runs once per query, only
over the physical tree, and only when CTE Producers/Consumers are present.
The set of queries that newly fall back to the Postgres planner is narrow
(replicated CTE Producer with a cross-slice Consumer) — these queries
previously hung, so any plan is an improvement.
**User-facing changes:** Queries matching the pattern above now complete
instead of hanging. Users will see
`INFO: GPORCA failed to produce a plan, falling back to planner` /
`DETAIL: Feature not supported: CTE Consumer placed on a different slice
than its replicated Producer` in those cases.
**Dependencies:** None.
### Checklist
- [x] Followed [contribution
guide](https://cloudberry.apache.org/contribute/code)
- [ ] Added/updated documentation
- [x] Reviewed code for security implications
- [ ] Requested review from cloudberry committers
### Additional Context
Cherry-picked from open-gpdb/gpdb#375 (commit
`3a9aebfe3afb27dd060c16b5cfa7932e7a2ed43f`).
Files changed:
- `src/backend/gporca/libgpopt/include/gpopt/base/CUtils.h`
- `src/backend/gporca/libgpopt/src/base/CUtils.cpp`
- `src/backend/gporca/libgpopt/src/translate/CTranslatorExprToDXL.cpp`
- `src/test/regress/{sql,expected}/qp_orca_fallback{,.out,_optimizer.out}`
- `src/test/regress/{sql,expected}/shared_scan{,.out,_optimizer.out}`
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