go-sql-driver/mysql

Implement cursor support

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#1053 opened on Jan 7, 2020

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database/sql issueenhancementhelp wanted

Description

Issue description

In some cases it might be undesirable to fetch a potentially huge resultset at once.

MySQL provides cursors for that in the binary protocol (prepared statements).

First, a cursor flag has to be set in COM_STMT_EXECUTE, then the result chunks can be requested with the COM_STMT_FETCH command.

Initially, we will probably only support forward-only and read-only cursors. However the question remains, trough what interface we make this feature available.

Contributor guide

Tech stack
gomysql
Domain
backenddatabase
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
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.
clear
Prerequisites
Go programmingMySQL protocol
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Implement cursor support by setting the cursor flag in COM STMT EXECUTE and using COM STMT FETCH. Refer to MySQL internals documentation (https://dev.mysql.com/doc/internals/en/com stmt execute.html and https://dev.mysql.com/doc/internals/en/com stmt fetch.html). The main question is the interface; consider forward only and read only cursors. Look at existing comments for design ideas.