pingcap/tidb

The point get executor and batch point get executor may not be thread safe

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#19,130 opened on Aug 11, 2020

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Description

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Issue https://github.com/pingcap/tidb/issues/16817 says

I guess there may exist other problems / panics behind this single symptom described in this issue, because PointGet now may be
 running in parallel with other goroutines(not only the main goroutine in this case, but other goroutines, e.g, workers of IndexJoin 
/ IndexHashJoin?), while the original implementation of its execution seems not to consider the possibility of concurrent running?
 We'd better do a full check of these potential concurrent situations to make sure PointGet is safe there.

For batchPointGetExecutor, the init flag is set using atomic operations, but the index field is not. Maybe we need to do more checks and tests to ensure these two executors are thread-safe.

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#sig-exec

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300

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  • @lzmhhh123

Contributor guide

Research direction
Inspect PointGet and BatchPointGet executors for thread safety. Focus on the `index` field in batchPointGetExecutor. Write tests with race detector to confirm.
Tech stack
go
Domain
backenddatabase
Issue type
Bug
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.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Needs investigation
Prerequisites
Goconcurrency
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35