Mryange opened a new pull request, #63713:
URL: https://github.com/apache/doris/pull/63713
### What problem does this PR solve?
Problem Summary:
Casting a JSON string with duplicated object keys to MAP kept all duplicated
entries because the string-to-complex cast path returned the generic wrapper
directly and skipped ColumnMap::deduplicate_keys(). This made string-to-map
casts inconsistent with MAP constructor semantics where the last value wins.
Reproduction SQL:
```sql
SELECT CAST('{"a":1,"a":2}' AS MAP<STRING,INT>);
SELECT size(CAST('{"a":1,"a":2}' AS MAP<STRING,INT>));
SELECT element_at(CAST('{"a":1,"a":2}' AS MAP<STRING,INT>), 'a');
SELECT map('a',1,'a',2);
SELECT size(map('a',1,'a',2));
SELECT element_at(map('a',1,'a',2), 'a');
```
Before this fix:
```text
{"a":1, "a":2}
2
1
{"a":2}
1
2
```
After this fix:
```text
{"a":2}
1
2
{"a":2}
1
2
```
This change wraps the string-to-map cast path with a map-key deduplication
step so duplicated keys are normalized after parsing from string. It also adds
regression coverage for the cast result, size, and element_at behavior on
duplicated keys.
### 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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