delta-io/delta

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

Open

#2,047 建立於 2023年9月12日

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 (1 留言) (0 反應) (0 負責人)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.

貢獻者指南

技術棧
java
領域
backend
議題類型
feature
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
3-5 days
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
fresh
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
mostly clear
前置要求
Scala/Java knowledgeDelta Kernel basicsExpression evaluation
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
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.