EeshanBembi opened a new pull request, #18137:
URL: https://github.com/apache/datafusion/pull/18137
Fixes #18020
## Summary
Enables `concat` function to concatenate arrays like `array_concat` while
preserving all existing string concatenation behavior.
**Before:**
```sql
SELECT concat([1, 2, 3], [4, 5]);
-- Result: [1, 2, 3][4, 5] ❌
```
**After**:
```sql
SELECT concat([1, 2, 3], [4, 5]);
-- Result: [1, 2, 3, 4, 5] ✅
```
Implementation
- Extended concat function signature to accept array types
- Added type detection in invoke_with_args() to delegate array operations
to Arrow
compute functions
- Enhanced type coercion to handle mixed array types and empty arrays
- Maintains full backward compatibility with string concatenation
Test Coverage
- ✅ Array concatenation: [1,2] + [3,4] → [1,2,3,4]
- ✅ Empty arrays: [1,2] + [] → [1,2]
- ✅ Nested arrays: [[1,2]] + [[3,4]] → [[1,2],[3,4]]
- ✅ String concatenation unchanged: 'hello' + 'world' → 'helloworld'
- ✅ Mixed type coercion: true + 42 + 'test' → 'true42test'
- ✅ Error handling: [1,2] + 'string' → Error
Approach Benefits
Function-level implementation vs planner replacement:
- Cleaner architecture (single responsibility)
- No planner complexity
- Better performance
- Easier testing and maintenance
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