pingcap/tidb

executor: avoid joiner to copying data when filter rows

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#12,030 opened on Sep 4, 2019

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help wantedsig/executiontype/enhancementtype/performance

Description

Feature Request

Is your feature request related to a problem? Please describe:

We can use the sel field in chunk.Chunk instead of copying data in baseJoiner.filter when filtering data in join executor

Describe the feature you'd like:

We can use the sel field in chunk.Chunk used in baseJoiner.filter

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

Contributor guide

Tech stack
go
Domain
backenddatabaseperformance
Issue type
feature
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
Basic knowledge of GoUnderstanding of TiDB's executorFamiliarity with chunk.Chunk and sel field
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Study the `baseJoiner.filter` function in `executor/joiner.go` and the `sel` field in `util/chunk/chunk.go`. Understand how data is currently copied and how using `sel` can avoid that. Implement the change to use `sel` in `filter`, ensuring no performance regressions. Add tests to verify correctness.
executor: avoid joiner to copying data when filter rows · pingcap/tidb#12030 | Good First Issue