pingcap/tidb

Support not null ScalarFunction.

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#9,965 建立於 2019年3月31日

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help wanted

描述

Feature Request

Describe the feature you'd like:

Currently, TiDB Don't have not null ScalarFunction, the implementation of not null is not (is null).

Separate implementation of not null must be better than the composed of two 2 ScalarFunction.

Next step: implement not null in TiKV coprocessor and push down.

貢獻者指南

技術棧
go
領域
databasebackend
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。
4
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。
over 1 week
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。
stale
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
Go programmingTiDB expression frameworkTiKV coprocessor basics
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。
10
研究方向
Examine how existing scalar functions like `is null` and `not` are implemented in TiDB's expression package (e.g., `expression/scalar function.go`). Design a new `not null` scalar function that performs the inverse of `is null`. Then implement the function and ensure it supports coprocessor pushdown to TiKV. Review the TiKV coprocessor code for adding new scalar functions, following the pattern of existing implementations.