terrymanu commented on issue #37431:
URL:
https://github.com/apache/shardingsphere/issues/37431#issuecomment-3673472779
## Problem Understanding
- Scenario: single database, single table (SET DEFAULT SINGLE TABLE
STORAGE UNIT = ds_0), no SQL Federation or sharding enabled. SQL is a standard
GROUP BY + HAVING with a correlated subquery whose WHERE references the outer
grouping column.
- Expected: behave like native PostgreSQL and push down successfully.
- Actual: in Proxy 5.5.2 (and ShardingSphere-JDBC, which shares the same
binder) binding fails with Unknown column 'ref_0.c13' in 'where clause', so it
never reaches the backend.
## Root Cause
- In infra/binder/core, HAVING binding passes only the projection-based
currentTableBinderContexts into the subquery’s outer context and omits the
FROM-generated tableBinderContexts (which contain outer aliases such as ref_0).
- When binding the subquery, the outer alias is invisible;
ColumnSegmentBinder then treats ref_0.c13 in the subquery WHERE as missing and
throws ColumnNotFoundException.
## Analysis
- The SQL is within ShardingSphere’s supported scope: single-table direct
pushdown should work, and the database itself executes it fine.
- Correlated subqueries in WHERE work because that path includes the FROM
context; the HAVING path misses it.
- Impact scope: all dialects (MySQL/PG/openGauss, etc.) in both Proxy and
JDBC modes can hit this binding defect.
## Conclusion (Fix Proposal & Invitation)
- This is a general binder gap for correlated subqueries in HAVING.
Proposal: when binding HAVING, merge the FROM tableBinderContexts together with
currentTableBinderContexts into the subquery’s outer context (align with the
WHERE path) so the subquery can resolve outer
aliases.
- Add regression tests in infra/binder for HAVING with correlated
subqueries referencing outer columns to ensure no ColumnNotFound and correct
pushdown.
- We warmly welcome community contributors to submit a PR to implement the
fix and the tests—your help to make this scenario solid is greatly appreciated!
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