andygrove opened a new issue, #3157:
URL: https://github.com/apache/datafusion-comet/issues/3157
## What is the problem the feature request solves?
> **Note:** This issue was generated with AI assistance. The specification
details have been extracted from Spark documentation and may need verification.
Comet does not currently support the Spark `array_position` function,
causing queries using this function to fall back to Spark's JVM execution
instead of running natively on DataFusion.
The `ArrayPosition` expression finds the position of the first occurrence of
a specified element within an array. It returns a 1-based index of the
element's position, or 0 if the element is not found in the array.
Supporting this expression would allow more Spark workloads to benefit from
Comet's native acceleration.
## Describe the potential solution
### Spark Specification
**Syntax:**
```sql
array_position(array, element)
```
```scala
// DataFrame API usage
import org.apache.spark.sql.functions._
df.select(array_position(col("array_column"), lit(value)))
```
**Arguments:**
| Argument | Type | Description |
|----------|------|-------------|
| array | ArrayType | The input array to search within |
| element | Any (matching array element type) | The element to find within
the array |
**Return Type:** `LongType` - Returns a 1-based position index as a long
integer, or 0 if the element is not found.
**Supported Data Types:**
- Array element types must be orderable (support comparison operations)
- The search element type must be compatible with the array's element type
through type coercion
- Null types are explicitly rejected and will cause a type mismatch error
**Edge Cases:**
- **Null array input**: Returns null due to `nullIntolerant = true`
- **Null search element**: Returns null due to `nullIntolerant = true`
- **Null elements in array**: Skipped during comparison, never match the
search element
- **Empty array**: Returns 0 (no elements to match)
- **Element type mismatch**: Compile-time error with detailed type mismatch
information
- **Multiple occurrences**: Only returns the position of the first occurrence
**Examples:**
```sql
-- Find position of element in array
SELECT array_position(array(312, 773, 708, 708), 414);
-- Returns: 0
SELECT array_position(array(312, 773, 708, 708), 773);
-- Returns: 2
SELECT array_position(array('a', 'b', 'c', 'b'), 'b');
-- Returns: 2 (first occurrence)
-- With null values
SELECT array_position(array(1, null, 3, null), 3);
-- Returns: 3
```
```scala
// DataFrame API examples
import org.apache.spark.sql.functions._
// Find position of specific value
df.select(array_position(col("numbers"), lit(42)))
// Find position with column reference
df.select(array_position(col("items"), col("search_value")))
// Using in filter conditions
df.filter(array_position(col("tags"), lit("important")) > 0)
```
### Implementation Approach
See the [Comet guide on adding new
expressions](https://datafusion.apache.org/comet/contributor-guide/adding_a_new_expression.html)
for detailed instructions.
1. **Scala Serde**: Add expression handler in
`spark/src/main/scala/org/apache/comet/serde/`
2. **Register**: Add to appropriate map in `QueryPlanSerde.scala`
3. **Protobuf**: Add message type in `native/proto/src/proto/expr.proto` if
needed
4. **Rust**: Implement in `native/spark-expr/src/` (check if DataFusion has
built-in support first)
## Additional context
**Difficulty:** Medium
**Spark Expression Class:**
`org.apache.spark.sql.catalyst.expressions.ArrayPosition`
**Related:**
- `array_contains` - Check if array contains an element (boolean result)
- `element_at` - Get element at specific position in array
- `array_remove` - Remove all occurrences of element from array
- `size` - Get the size/length of an array
---
*This issue was auto-generated from Spark reference documentation.*
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