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MyIsam crashes
Posted by: Lars Thiele
Date: April 29, 2005 11:40AM

Hi,

I have a big problem with using MyIsam tables with more than one blob field.
I am using the MySQL C API, and Mysql server 4.1.10 on a Suse 9.2.
My table contains 12 blob fields and some varchar fields, with a total size of 600MB. Here is the result of a describe table statemanet:
+--------------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------------+------------------+------+-----+---------+----------------+
| bayesianId | int(20) unsigned | | PRI | NULL | auto_increment |
| imageId | int(20) unsigned | | MUL | 0 | |
| ehd_vector | blob | | | | |
| ehd_vector_length | int(11) | | | 0 | |
| ehd_n | int(11) | YES | | 0 | |
| ehd_mean | blob | | | | |
| ehd_variance | blob | | | | |
| htd_vector | blob | | | | |
| htd_vector_length | int(11) | | | 0 | |
| htd_n | int(11) | YES | | 0 | |
| htd_mean | blob | | | | |
| htd_variance | blob | | | | |
| cld_vector | blob | | | | |
| cld_vector_length | int(11) | | | 0 | |
| cld_n | int(11) | YES | | 0 | |
| cld_mean | blob | | | | |
| cld_variance | blob | | | | |
| lald_vector | blob | | | | |
| lald_vector_length | int(11) | | | 0 | |
| lald_n | int(11) | YES | | 0 | |
| lald_mean | blob | | | | |
| lald_variance | blob | | | | |
| source | varchar(255) | | MUL | | |
+--------------------+------------------+------+-----+---------+----------------+

The problem that occurs is:
1. When doing a SELECT on that tabel I randomly get the error 127. (the user that does the selects does not have writing permissions)
2. When doing a mysql check table TABLE, the table gets marked as crashed.
3. Repairing results in data loss.

BUT: when I am clearing the systems memory (virtual & real, by doing a restart of my system or using a c++ program allocating a lot of memory) before doing a check table, every thing is fine. And the error disappeared!

Flushing the tables or reseting the mysqld doesn't help anything.
I upgraded from a MySQL server version 4.0.x, there the error appeared much more often.

I did a memory test, with no error resulting!

What could be the problem (the hardware, suse 9.2, MySQl itself)?

Thanks a lot.

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MyIsam crashes
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April 29, 2005 11:40AM
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