databendlabs/databend

Feature: add list function like duckdb

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#10,497 opened on Mar 11, 2023

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C-featuregood first issue

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Description

Summary list(a) fill rows of column a into a list/array also support group by and order by eg.

D select list(i)from range(10)t(i);
┌────────────────────────────────┐
│            list(i)             │
│            int64[]             │
├────────────────────────────────┤
│ [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] │
└────────────────────────────────┘
D select i%3,list(i)from range(10)t(i)group by i%3;
┌─────────┬──────────────┐
│ (i % 3) │   list(i)    │
│  int64  │   int64[]    │
├─────────┼──────────────┤
│       0 │ [0, 3, 6, 9] │
│       1 │ [1, 4, 7]    │
│       2 │ [2, 5, 8]    │
└─────────┴──────────────┘

Contributor guide

Research direction
Implement the list() aggregate function similar to DuckDB's list(). Study existing aggregate functions in Databend (e.g., groupArray) and how they handle group by and order by. Then write code to collect column values into an array with optional ordering.
Tech stack
rustsql
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
RustSQLGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75