[Feature] Support Spark expression: array_position

[andygrove]

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:

array_position(array, element)

// 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:

-- 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

// 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 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

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This issue was auto-generated from Spark reference documentation.

[navinvishy]

@andygrove I'd be interested in working on this if that's ok.