Fix lambda return type coercion

[tdcmeehan]

Description

Currently, Presto won't apply any coercion on the return type within a lambda. We should make it more flexible.

Motivation and Context

Recently, array_sort with transform was added to Presto, and this can cause conflicts with the older comparator approach.

Impact

Fix issues with array_sort and potential future issues with lambdas.

Test Plan

Included unit tests.

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Release Notes

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== RELEASE NOTES ==

[sourcery-ai]

Reviewer's Guide

Enhance lambda return type handling by catching argument count mismatches, applying coercion within ExpressionAnalyzer when actual and expected return types differ, enabling return type coercion in the SignatureBinder, updating comparator function signatures to use bigint, and adding targeted tests for array_sort lambda return type coercion.

File-Level Changes

Change	Details	Files
Implement lambda return type coercion in ExpressionAnalyzer	Wrap inner lambda analysis in try/catch to handle LambdaArgumentCountMismatchException Return a generic unknown type signature for invalid lambdas After processing lambdas, detect return type mismatches and insert expression coercion when permissible Update lambda expression type to the expected FunctionType	ExpressionAnalyzer.java
Introduce LambdaArgumentCountMismatchException	Add new exception class extending SemanticException for mismatched lambda arguments Replace direct SemanticException throw in visitLambdaExpression with the new exception	LambdaArgumentCountMismatchException.java ExpressionAnalyzer.java
Enable lambda return type coercion in SignatureBinder	Allow coercion in appendTypeRelationshipConstraintSolver and appendConstraintSolvers for lambda return types Remove the previous hard stop preventing function type coercion	SignatureBinder.java
Update comparator function return type annotations	Change @SqlType for ComparatorXxxLambda parameters from int to bigint across all sort methods	ArraySortComparatorFunction.java
Add tests for array_sort lambda return type coercion	Create testArraySortLambdaReturnTypeCoercion with various assertFunction cases covering coercion scenarios	TestArrayOperators.java

Possibly linked issues

• Add simple HashAggregation #1: The PR directly fixes the array_sort lambda comparator signature to accept bigint, resolving the type mismatch error described in the issue.

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[kgpai]

@tdcmeehan This is a simple fix if you change the Velox lambda function signature to return integer (from bigint). We validated that it works with the side car.

[tdcmeehan]

@tdcmeehan This is a simple fix if you change the Velox lambda function signature to return integer (from bigint). We validated that it works with the side car.

@kgpai is anyone working to add that to Velox?

[Dilli-Babu-Godari]

@tdcmeehan This is a simple fix if you change the Velox lambda function signature to return integer (from bigint). We validated that it works with the side car.

I agree — changing the Velox lambda function signature to return integer instead of bigint is a straightforward fix. That said, I also think we should support type coercion in lambdas more generally, so this kind of mismatch doesn’t surface again.

[kgpai]

@tdcmeehan Yes I am working on it - will have a PR out soon.

[tdcmeehan]

Sounds good, so I'll remove the first commit from this PR.