pingcap/tidb

reduce optimizer cpu usage when handling very large IN(...) expression

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#22,412 opened on Jan 15, 2021

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help wantedpriority/P1sig/plannertype/enhancement

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Description

Development Task

When handling expression with a very large IN(...) expression, the optimizer could use too much CPU. image

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Contributor guide

Research direction
Profile the CPU usage for large IN lists and identify hotspots in the optimizer code.
Tech stack
go
Domain
backend
Issue type
Performance
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
Godatabase optimizer internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30