morrySnow opened a new pull request, #67732:
URL: https://github.com/apache/doris/pull/67732
## Problem
Counting a projected alias over a nullable indexed column can return an
incorrect non-zero result when the filter retains only null rows. Mixing the
alias count with `COUNT(*)` or another count exposes the problem:
```sql
SELECT COUNT(x), COUNT(*)
FROM (SELECT k AS x FROM t WHERE k IS NULL) q;
```
For two matching null rows, the correct result is `(0, 2)`, but the
storage-layer index-count path can return `(2, 2)`.
## Root cause
The FE implementation rule validates `IS NULL` and OR predicates before
pushing count aggregation to the storage layer. In the Project variant, this
validation used the aggregate-side alias slot, while the filter below the
Project refers to the source slot. Their expression IDs differ, so the
null-safety guard did not recognize that the filter and `COUNT` referenced the
same nullable value.
The rule normalized the aggregate argument to the source slot only later,
after the safety decision had already been made.
## Reproduction
```sql
CREATE TABLE t (
id INT NOT NULL,
k INT NULL,
INDEX idx_k (k) USING INVERTED
)
DUPLICATE KEY(id)
DISTRIBUTED BY HASH(id) BUCKETS 1
PROPERTIES ("replication_num" = "1");
INSERT INTO t VALUES (1, NULL), (2, NULL), (3, 1);
SELECT COUNT(x), COUNT(*)
FROM (SELECT k AS x FROM t WHERE k IS NULL) q;
SELECT COUNT(x), COUNT(id)
FROM (SELECT k AS x, id FROM t WHERE k IS NULL) q;
```
Before this change, both queries return `(2, 2)` and the plan contains
`pushAggOp=COUNT_ON_INDEX`. Both queries should return `(0, 2)`.
## Fix
Normalize aggregate arguments through the Project before collecting the
slots used by the predicate safety checks. The count slots and filter slots are
now compared in the same source expression-ID domain. If `IS NULL` targets a
counted source slot, the FE rejects the index-count pushdown and preserves the
column's null values.
This change is limited to the FE planner.
## Tests
- Added a FE plan test for `COUNT(projected_alias) + COUNT(*)` above an `IS
NULL` filter, verifying that the count-on-index implementation rule is rejected.
- Ran `PhysicalStorageLayerAggregateTest`: 7 tests passed.
- Deployed the FE to a local sandbox and reran both SQL reproductions. They
return `(0, 2)`, and the scan plan reports `pushAggOp=NONE`.
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