jaredmdobson opened a new issue, #70448:
URL: https://github.com/apache/doris/issues/70448
### Search before asking
- [x] I searched the issues and found no similar issues.
### Version
4.1.5 (apache/doris:fe-4.1.5 / be-4.1.5 images)
### What's wrong?
Wrong result. A lambda expression over the nullable side of a `LEFT JOIN` is
evaluated below the join, so NULL-extended rows get NULL instead of the
expression's value. The same expression without a lambda is correct.
`EXPLAIN SHAPE PLAN` shows the projection holding `array_filter(...)` placed
under the join, on the scan of `b`:
```
PhysicalResultSink
--PhysicalProject
----hashJoin[LEFT_OUTER_JOIN broadcast] hashCondition=((a.id = b.id))
otherCondition=()
------PhysicalProject
--------PhysicalOlapScan[a]
------PhysicalProject
--------PhysicalOlapScan[b]
```
### What you expected to happen
Row 2 (no match in `b`): `filtered = ["n"]` and `mapped = ["N"]`, the same
as `plain` and as the expression over a NULL literal (`SELECT array_filter(x ->
x != '', IF(NULL IS NULL, ['n'], NULL))` returns `["n"]`).
Actual:
```
id plain filtered mapped
1 ["p", ""] ["p"] ["P", ""]
2 ["n"] NULL NULL
```
### How to reproduce
```sql
DROP DATABASE IF EXISTS lambda_null FORCE;
CREATE DATABASE lambda_null;
USE lambda_null;
CREATE TABLE a (id INT) DUPLICATE KEY(id) DISTRIBUTED BY HASH(id) BUCKETS 1
PROPERTIES ("replication_num" = "1");
CREATE TABLE b (id INT, arr ARRAY<STRING>) DUPLICATE KEY(id) DISTRIBUTED BY
HASH(id) BUCKETS 1 PROPERTIES ("replication_num" = "1");
INSERT INTO a VALUES (1), (2);
INSERT INTO b VALUES (1, ['p', '']);
SELECT a.id,
IF(b.arr IS NULL, ['n'], b.arr) AS
plain,
array_filter(x -> x != '', IF(b.arr IS NULL, ['n'], b.arr)) AS
filtered,
array_map(x -> upper(x), IF(b.arr IS NULL, ['n'], b.arr)) AS
mapped
FROM a LEFT JOIN b ON b.id = a.id
ORDER BY a.id;
```
### Anything Else?
Possibly related to #70447 (the lambda argument slot is a
`SlotNotFromChildren`, so the expression may look like it only reads `b`).
Workaround: no lambda, e.g. `array_remove(arr, '')` instead of `array_filter(x
-> x != '', arr)`.
### Are you willing to submit PR?
- [ ] Yes I am willing to submit a PR!
### Code of Conduct
- [x] I agree to follow this project's Code of Conduct
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