pingcap/tidb

The query in slow log can't be parsed when there is single comment in sql

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#30,886 opened on Dec 20, 2021

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help wantedseverity/moderatesig/sql-infratype/bug

Description

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

If we execute the sql with tidb, and image it is a slow query.

select count(*) from t x ,t y
-- condition
where x.a<y.a
and x.a is not null -- comment

The query recorded in tidb slow log is select count(*) from t x ,t y -- condition where x.a<y.a and x.a is not null -- comment; , and we can't parse the sql correctly because we can't identify which sentences are commented. Compared with tidb，the mysql slow query in the log is

select count(*) from t x ,t y
-- condition
where x.a<y.a
and x.a is not null -- comment;

2. What did you expect to see? (Required)

same with mysql

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

master

Contributor guide

Tech stack
gosql
Domain
database
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.
1-3 hours
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 parsing basicsGo programming
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Investigate the slow log parsing logic in TiDB's parser package (likely in the 'parser' directory). The issue is about handling line comments in SQL queries. Look at how the slow log stores queries and ensure that comments are preserved correctly. Check existing tests for slow log parsing and add a test case for this scenario.