pingcap/tidb

Accelerate FindColumn when table has huge number of columns

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#11,151 opened on Jul 9, 2019

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help wantedtype/enhancementtype/performance

Description

Feature Request

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

will be frequently called when build query plan or build insert value list.

now it uses linear search to find column info match target name....

when the table has limitation columns it works well...

but when table got many columns (e.g. 200+ columns), upper logic will find 200 columns to do linear search in 200 items.

image

Describe the feature you'd like:

maybe we should adaptively replace a linear search with another method when table has many columns

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
Go programmingTiDB internalsalgorithm optimizationperformance profiling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
The issue points to two functions: FindCols in table/column.go and FindColumn in expression/schema.go. Both currently use linear search to find column info by name. The goal is to replace linear search with a more efficient method (e.g., hash map) when the number of columns is large. Research should start by understanding the current implementation and the data structures used. Then, consider implementing an adaptive approach: keep linear search for small column counts and switch to a map or sorted slice with binary search for larger counts. Profile the performance impact on query planning and insert value building. Check the three comments for any additional insights or suggestions.