pingcap/tidb

enhance `explain analyze` to show more runtime statistics about each operator

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#8,213 opened on Nov 7, 2018

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help wantedsig/executiontype/enhancement

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Description

With this enhancement, we can identify:

  • the true selectivity for each operator
  • how long it takes to gain the first output record for each operator.

With the help of this kind of information, we can know whether the execution plan is wrong, and how the incorrect or inefficient plan was generated.

Contributor guide

Research direction
Investigate the explain analyze code path in TiDB's executor package to add runtime statistics for each operator, focusing on selectivity and time to first row output.
Tech stack
go
Domain
databasebackend
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.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GoSQLdatabase internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40