pingcap/tidb

blob/text/int length isn't accuracy in column metadata

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#7,465 opened on Aug 22, 2018

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help wantedtype/compatibility

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Description

  1. What did you do?

connection tidb with --column-type-info

create table bitest(b blob(2));
select * from bitest;
  1. What did you expect to see?
Length:     255
  1. What did you see instead?
Length:     8
  1. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?
2.0.6

ref #7463

Contributor guide

Research direction
Inspect how column type info length is computed for blob/text types, particularly the handling of the 'blob length' parameter in the MySQL protocol. Look at the relevant code in the TiDB server that sends column metadata, and compare with MySQL's behavior.
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.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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
GoMySQL protocol knowledge
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35