pingcap/tidb

Add new agg function like `SKEW` or `SKEWNESS` to show the skewness of the expression/column.

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#24,721 opened on May 18, 2021

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Description

Feature Request

Is your feature request related to a problem? Please describe:

A aggregate function to show the skewness of the data. To better know the distribution.

Describe alternatives you've considered:

Snowflake, SAS, influxdb, IBM, SKEWNESS_SAMP and SKEWNESS_POP in oracle.

Teachability, Documentation, Adoption, Migration Strategy:

Contributor guide

Research direction
Examine existing aggregate functions (e.g., AVG, STDDEV) in TiDB's expression package. Understand the skewness formula (third standardized moment). Implement the function following the pattern of other statistical aggregates.
Tech stack
go
Domain
database
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GoSQL
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65