pingcap/tidb

Investigate and propose Adaptive Join

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#14,408 opened on Jan 9, 2020

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help wantedsig/executionsig/plannertype/enhancement

Description

Feature Request

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

Sometimes optimizer need defer the choise of Hash Join or Index Nested loops Join because it does not have a deterministic statistics.

Describe the feature you'd like:

We need someone who is familiar with planner and executor to drive and propose a plan, and see how we can be benefited with Adaptive Join.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

Contributor guide

Tech stack
gosql
Domain
backenddatabaseperformance
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
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.
mostly clear
Prerequisites
TiDB planner knowledgeTiDB executor knowledgeJoin algorithm understandingQuery optimization experience
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
5
Research direction
Research the adaptive join implementations in SQL Server and Oracle as referenced. Investigate TiDB's current planner (e.g., planner/core) and executor (executor) codebase to propose a design for adaptive join that defers join type choice based on runtime statistics. Engage with maintainers on the design proposal before implementation.
Investigate and propose Adaptive Join · pingcap/tidb#14408 | Good First Issue