[Feature] Support Spark expression: array_exists #3149

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_exists function, causing queries using this function to fall back to Spark's JVM execution instead of running natively on DataFusion.

The ArrayExists expression checks whether any element in an array satisfies a given predicate function. It applies a lambda function to each element of the array and returns true if at least one element makes the predicate evaluate to true.

Supporting this expression would allow more Spark workloads to benefit from Comet's native acceleration.

Describe the potential solution

Spark Specification

Syntax:

EXISTS(array, lambda_function)

Arguments:

Return Type: BooleanType - Returns true if any element satisfies the predicate, false if none do, or null in certain null-handling scenarios.

Supported Data Types:

• Input: Any ArrayType with elements of any data type
• Lambda function must return a boolean result
• Supports arrays with nullable elements

Edge Cases:

• Null array input: Returns null if the input array itself is null
• Empty array: Returns false for empty arrays
• Null lambda results: When followThreeValuedLogic is true and lambda returns null for some elements but no element returns true, the overall result is null
• Legacy mode: When followThreeValuedLogic is false, null lambda results are ignored and only affect final result if no true value is found
• Nullable elements: Properly handles null elements within the array by passing them to the lambda function

Examples:

-- Check if any element is null
SELECT EXISTS(array(1, 2, 3), x -> x IS NULL);
-- Returns: false

-- Check if any element is greater than 2
SELECT EXISTS(array(1, 2, 3), x -> x > 2);
-- Returns: true

-- Check with null elements
SELECT EXISTS(array(1, null, 3), x -> x IS NULL);
-- Returns: true

// DataFrame API usage
import org.apache.spark.sql.functions._

df.select(exists(col("array_column"), x => x > lit(10)))

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.ArrayExists

Related:

• ArrayForAll - Checks if all elements satisfy a predicate
• ArrayFilter - Filters array elements based on a predicate
• ArrayTransform - Transforms array elements using a lambda function

This issue was auto-generated from Spark reference documentation.