delta-io/delta

[Feature Request][Kernel] Support implicit cast for `DefaultExpressionEvaluator` output.

Open

#2,047 创建于 2023年9月12日

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 (1 评论) (0 反应) (0 负责人)Scala (8,807 star) (2,100 fork)batch import
enhancementgood first issuekernel

描述

Feature request

Which Delta project/connector is this regarding?

  • Spark
  • Standalone
  • Flink
  • Kernel
  • Other (fill in here)

Overview

Currently ExpressionHandler.getEvaluator takes an expected output type as argument. The comment here is to handle the implicit cast incase the expression output can be safely cast to the asked output type.

贡献者指南

技术栈
java
领域
backend
议题类型
feature
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
3
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
3-5 days
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
fresh
清晰度议题是否清楚说明期望改动、验收标准和下一步。
mostly clear
前置要求
Scala/Java knowledgeDelta Kernel basicsExpression evaluation
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
35
研究方向
The issue requests support for implicit casting in `DefaultExpressionEvaluator` output. Start by examining `ExpressionHandler.getEvaluator` method and the linked comment in PR #1997 (delta/pull/1997/files#r1312397301). Investigate how the expected output type is currently used and where safe casting could be inserted. Look for existing type conversion utilities in the Delta Kernel codebase. The goal is to implement automatic casting when the expression output type can be safely converted to the requested type.