pingcap/tidb

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

Open

#8,213 opened on Nov 7, 2018

View on GitHub
 (2 comments) (0 reactions) (1 assignee)Go (40,090 stars) (6,186 forks)batch import
help wantedsig/executiontype/enhancement

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

Tech stack
gosql
Domain
databaseperformance
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.
3-5 days
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
GoQuery execution conceptsTiDB architecture
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Examine the current implementation of 'explain analyze' in TiDB's executor package. Review how operators report statistics and identify where to add selectivity and first output time measurements. Look for existing runtime stats structures (e.g., in executor/executor.go) and propose modifications to store and display the new metrics.