pingcap/tidb

executor.Next() should not call chid.Open() or child.Close()

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#4,983 opened on Nov 2, 2017

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help wanted

Description

calling Open() or Close() during Next() makes our executors un-maintainable, for example, if we comment out the following lines then make test, our ut failes ... https://github.com/pingcap/tidb/blob/0616a2fd1511e2206086c212261d93b1106605c7/executor/executor.go#L345

or https://github.com/pingcap/tidb/blob/0616a2fd1511e2206086c212261d93b1106605c7/executor/join.go#L88

Open is used to initialize executors and allocate resources for every executor Close is used to deallocate the resource adopted by every executor, avoid memory leak

Contributor guide

Tech stack
go
Domain
backend
Issue type
bug
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.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Go programmingunderstanding of executor lifecycle
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Examine the references in executor/executor.go and executor/join.go to understand the current pattern. Determine the correct places to call Open and Close without violating the Next contract. Ensure that existing tests pass after the refactoring, as noted in the issue that tests fail with current code. Consider the wider executor hierarchy to maintain consistency.