pingcap/tidb

Error should be thrown when there's ASC/DESC with GROUP BY clause

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#10,522 opened on May 17, 2019

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help wantedpriority/P4sig/plannertype/feature-request

Description

Bug Report

Please answer these questions before submitting your issue. Thanks!

  1. What did you do? If possible, provide a recipe for reproducing the error.
CREATE TABLE t1 (id INTEGER, sex CHAR(1));
SELECT sex, AVG(id), ROW_NUMBER() OVER w FROM t1
GROUP BY sex ASC
WINDOW w AS () ORDER BY sex DESC;
  1. What did you expect to see?

Error ASC or DESC with GROUP BY isn't allowed with window functions; put ASC or DESC in ORDER BY is thrown.

  1. What did you see instead?

Execute successfully with no warning.

  1. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

Contributor guide

Tech stack
gosql
Domain
backenddatabase
Issue type
bug
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.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
SQL GROUP BY and window functionsGo language basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
The issue is that TiDB should throw an error when ASC/DESC is used with GROUP BY in the presence of window functions. The fix requires locating where the SQL query is parsed and validated. The parser or planner likely accepts this syntax erroneously. Examine the parser files (e.g., `parser/ast/select.go`) and the planner rules (e.g., `planner/core/rule aggregation push down.go`) to add a check that rejects such queries. Look at similar error messages in the codebase for reference.