MySQL Bugs: #21255: alter table varchar(255) to char don't set EndOfString character

Bug #21255	alter table varchar(255) to char don't set EndOfString character
Submitted:	24 Jul 2006 16:12	Modified:	9 Aug 2006 13:51
Reporter:	patrick Blesson	Email Updates:
Status:	Not a Bug	Impact on me:	None
Category:	MySQL Cluster: Cluster (NDB) storage engine	Severity:	S3 (Non-critical)
Version:	MYSQL V51 (5.1.12-BETA)	OS:	Linux vm10 2.4.20-28.9 #1 Thu D
Assigned to:	Geert Vanderkelen	CPU Architecture:	Any
Tags:	alter, char, table, varchar

Description:
This test is realized in V50(V5.1.2 drop14) and in V51(V5.1.12_beta)
in both delivery test is not-satisfactory

test log file of following actions is linked as res.txt file

-Create a database with a shema which contain a vvchar column of type VARCHAR(255)
-populate database
shema table is createtable.sql linked file
source of population is basic-type-popul.cpp linked file
-reading vchar population is OK
source of read is basic-read-read.cpp linked file
read result is readres1.txt
-alter table of varchar to CHAR(255)
altering seems OK
altering command is :
/usr/mysql/bin/mysql -D hlr -e "alter table IMSI modify vvchar CHAR(255);"
see test test linked shell file : run
-reading again vvchar population with CHAR type is KO
source of read is basic-read-read.cpp linked file
read result is readres2.txt
altering is OK but reading of vvchar value is false because
!!! string is padded with blank(h'20) by mysql alter function without EndOfString character !!!
(maybe alter table command needs to specify "endOfString character" to be able to set it after significant character of string using previous length of string)
(Alcatel uses '00' or '\0')
-update of altered column is OK
source of population is basic-type-update-newColumn.cpp linked file
-reading updated vchar population is OK
source of read is basic-read-read.cpp linked file
read result is readres3.txt

How to repeat:
create a cluster
create a shema with a varchar(255) column
set a value to this column (ex : size=28 string='French CHEESE with Jam&Salad')
read value OK
alter table this column to char(255)
read value result is : "French CHEESE with Jam&Salady?/%_-3u-vènè_432ç)çij.."
awaiting string 'French CHEESE with Jam&Salad''\0'

Suggested fix:
write a EndOfString char ('\0') at the end of string :   String[size]='\0'

Thank you for a problem report. Isn't it a duplicate of bug #21254?

answer to [24 Jul 18:26] Valeriy Kravchuk
    > Thank you for a problem report. Isn't it a duplicate of bug #21254?

No: there is a bit difference, we try both altering table : 
      CHAR  to varchar, and
      varchar to CHAR

in both tests there is some problem,  but not exactly the same!
-by altering char to varchar we expected that mysql   sets  correctly size attribut of new varchar string
-by altering varchar to char, we expected that mysql  adds an EndOfString char ('\0')    at old size position in new fixed length string

Best regards
Patrick

Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://dev.mysql.com/doc/ and the instructions on
how to report a bug at http://bugs.mysql.com/how-to-report.php

Additional info:
Trailing spaces are kept for CHAR fields and no \0 will be put in to denote the end of the string. This is expected behaviour. Removing of trailing spaces should be done in the NDB API application or using VARCHAR.