StarRocks/starrocks

Support using JSON as GROUP BY

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#62502 opened on Aug 29, 2025

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 (4 comments) (0 reactions) (1 assignee)Java (5,717 stars) (1,246 forks)batch import
good first issuetype/enhancement

Description

Enhancement

MySQL root@127.1:d1> select event_date from tjson group by event_date;
(1064, 'Getting analyzing error. Detail message: Type (nested) percentile/hll/bitmap/json not support group-by.')

JSON is currently not supported in the GROUP BY clause, but enabling this functionality could be beneficial for certain scenarios.

To implement GROUP BY support for JSON, a stable hash function and comparison function are required. This can be achieved using asymmetric hash mixing techniques, such as XOR, which is already implemented in JsonValue::hash.

Contributor guide

Tech stack
javasql
Domain
databaseperformance
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
StarRocks internalsJSON data typesHashing techniques
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate the current implementation of JsonValue::hash in the StarRocks codebase (likely in the C++ backend). Understand how asymmetric hash mixing is implemented and extend the GROUP BY operator to support JSON type by using that hash function. Also need a comparison function. Check if any existing similar implementations for other types can serve as a template. Refer to the issue comments for any additional maintainer guidance.