starocean999 opened a new pull request, #67362:
URL: https://github.com/apache/doris/pull/67362
### What problem does this PR solve?
Issue Number: close #xxx
Related PR: #xxx
Problem Summary:
Given a sync materialized view on `sync_tz_base`:
```sql
CREATE MATERIALIZED VIEW sync_tz_day AS
SELECT date_trunc(ts, 'day') AS day_ts, sum(v) AS day_sum
FROM sync_tz_base WHERE ts IS NOT NULL
GROUP BY date_trunc(ts, 'day');
```
the following query fails during planning with an NPE:
```sql
SELECT CAST(date_trunc(ts, 'day') AS STRING) AS day_ts, SUM(v)
FROM sync_tz_base WHERE ts IS NOT NULL
GROUP BY date_trunc(ts, 'day');
```
```
java.lang.NullPointerException: Cannot invoke
"org.apache.doris.analysis.Expr.getChildren()" because "root" is null
at org.apache.doris.analysis.Expr.extractSlots(Expr.java:173)
at
org.apache.doris.nereids.glue.translator.PhysicalPlanTranslator.visitPhysicalProject(PhysicalPlanTranslator.java:2173)
```
**Root cause**
In `AbstractMaterializedViewAggregateRule.aggregateRewriteByView`, the group
by keys of the rewritten aggregate were collected from the query **top plan**
output expressions. For a `project -> aggregate` structure,
`topPlanSplitToGroupAndFunction` classifies the derived projection
`cast(date_trunc(ts, 'day') AS STRING)` as a group-by expression, because it is
derived from the real group key. This derived projection was then wrongly added
as a group by key of the rewritten aggregate:
```
finalGroupExpressions = [cast(day_ts#7 as TEXT) AS #9, day_ts#7]
finalOutputExpressions = [cast(day_ts#7 as TEXT) AS #9, sum(day_sum#8) AS
#10]
```
This led to two problems:
1. A redundant group by key `cast(day_ts#7 as TEXT)` which is only a
projection of the real group key `day_ts#7`.
2. The real group key `day_ts#7` was added by the group-by compensation
logic but was **not** present in the aggregate output expressions, so the top
project referenced a slot that the physical aggregate never produced, causing
the `"root" is null` NPE during physical plan translation.
**Fix**
The rewritten aggregate is now built directly from the query bottom
aggregate:
- The group by keys are the query bottom aggregate's group by expressions
rewritten against the MV scan (always correct, so the previous group-by
compensation is no longer needed).
- The aggregate output contains the rewritten group keys and the rolled-up
aggregate functions.
- The query top plan output expressions — including derived projections of
group keys such as `cast(date_trunc(ts, 'day') AS STRING)` — are recomputed by
a `LogicalProject` above the rewritten aggregate when they cannot be produced
by the aggregate directly.
After the fix the rewritten plan is valid and the query returns correct
results:
```
Project [cast(day_ts#7 as TEXT) AS day_ts#3, sum(day_sum#8) AS SUM(v)#4]
Aggregate [group by [day_ts#7], output [day_ts#7, sum(day_sum#8)]]
MVScan(sync_tz_day)
```
### Release note
None
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [ ] Regression test
- [ ] Unit Test
- [ ] Manual test (add detailed scripts or steps below)
- [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
- [ ] Previous test can cover this change.
- [ ] No code files have been changed.
- [ ] Other reason <!-- Add your reason? -->
- Behavior changed:
- [ ] No.
- [ ] Yes. <!-- Explain the behavior change -->
- Does this need documentation?
- [ ] No.
- [ ] Yes. <!-- Add document PR link here. eg:
https://github.com/apache/doris-website/pull/1214 -->
### Check List (For Reviewer who merge this PR)
- [ ] Confirm the release note
- [ ] Confirm test cases
- [ ] Confirm document
- [ ] Add branch pick label <!-- Add branch pick label that this PR should
merge into -->
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