Bug #64042 when table has LONGBLOB is reading of other columns extremly slow

• Submitted: 16 Jan 2012 12:21
• Modified: 16 Feb 2012 13:45
• Reporter: Petr Svec
• Status: No Feedback
• Category: MySQL Server: MyISAM storage engine
• Severity: S1 (Critical)
• Version: 5.1, 5,5
• OS: Any
• CPU Architecture: Any
• Tags: BLOB, MySQL, SELECT, speed

[16 Jan 2012 12:21] Petr Svec

Description:

please solve bug on mysql.

table xxx 
-> id primary key 
-> name varchar 255 
-> data longblob

when I store to this table 100 files, each 100MB table would have 10GB

and than try to select any row...
 it takes to much

SELECT name FROM xxx WHERE id = 50 LIMIT 1; 
takes about 15 second

my problem is probably in that, mysql reads whole line before it return only name thats have 255 characters ... so when I want list names of (100) files mysql reads 10 GB !!! and return about 2 KB !!! result

How to repeat:
try create mentioned table and load any data

then

SELECT name FROM xxx;
it would take about 300 seconds

[16 Jan 2012 13:45] Valeriy Kravchuk

Please, send the output of:

show table status like 'xxx'\G

for the table in question. Also, try to use CHAR(255) instead of VARCHAR(255) and check if this makes any difference...

[17 Feb 2012 1:00] Bugs System

No feedback was provided for this bug for over a month, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".