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Re: Randomly slow Insert / Update on small table
Posted by: Sebastian Hamann
Date: October 30, 2009 08:00AM

Hello Rick,

thanks for you answer, I'll give some answers to your additionally questions and will get my team to work on the rest.

* Query cache? How much is allocated to it? Is it turned on?
* SHOW VARIABLES LIKE "query%";
* Don't know that it will solve your problem, but please try changing to
* query_cache_type = OFF

mysql> show variables like '%query%';
+------------------------------+---------------------------------------------+
| Variable_name                | Value                                       |
+------------------------------+---------------------------------------------+
| ft_query_expansion_limit     | 20                                          | 
| have_query_cache             | YES                                         | 
| long_query_time              | 1.000000                                    | 
| query_alloc_block_size       | 8192                                        | 
| query_cache_limit            | 1048576                                     | 
| query_cache_min_res_unit     | 4096                                        | 
| query_cache_size             | 1073741824                                  | 
| query_cache_type             | ON                                          | 
| query_cache_wlock_invalidate | OFF                                         | 
| query_prealloc_size          | 8192                                        | 
| slow_query_log               | OFF                                         | 
| slow_query_log_file          | /local/rg-mysql_master/data/mysqld-slow.log | 
+------------------------------+---------------------------------------------+
12 rows in set (0.00 sec)

It's on, we'll try turning it off, I'll report back when we tested that.

* Unrelated notes:
* set('yes','no') -- perhaps you meant ENUM, not SET. Or can it really be both yes and no?

Ups, haven't spotted that one, no of course not, we'll change that.

* How many queries per second are you running? (Questions/Uptime).
| Queries                           | 521936097    | 
| Questions                         | 492491898    | 
| Uptime                            | 782270       |

~667 queries/sec
~630 question/sec

* I see 6 indexes, each with a single field. Sometimes that indicates the the author does not know the power of "compound indexes".

We have discussed this. We'll probably even drop 4 of those 6 indexes, as they aren't realy good ones (to small variability(?) of values). As the table isn't that big, it shouldn't pose a problem, at least not for further debugging processes.

* Is MySQL 64-bit? Some of the settings might cause trouble in 32-bit.

| basedir                                 | /local/rg-mysql_master/bin/mysql-5.1.36-solaris10-x86_64/                                 |

I pretty darn hope so, but I'll get my team to double check it.


* Oh!
* | innodb_log_file_size | 67108864 |
* | innodb_log_files_in_group | 48 |
* I've never seen that second value be anything other than 2 or 3. A guess: 48 is not good. Plz try changing it thus:

Ok, we'll do so. I did some research but couldn't find anything precise about that setting. Do I understand this correctly?: This is the number of innodb bin log files MySQL keeps and rotates through? So after each backup they are pretty worthless, aren't they?

Oh well, as I said, we'll go ahead and test your ideas, I'll report back on monday with any results we got.

Regards,
Sebastian

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Re: Randomly slow Insert / Update on small table
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