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I'm using Mysql Server 5.6.15 and i have a huge database with many complex queries.

it seems that when I run the query the first time it takes X amount of time.

when I execute it again it takes less then X time. which means that something was cached.

I want to be able to performance test my queries in order to improve them regardles of caching.

is there a way to disable all caching types in mysql in order for me to properly test the execution time of my queries?

any information regarding the issue would be greatly appreciated.

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query_cache_type is set to 0, which means off. are there other caching mechanisms to be considered here? –  ufk Mar 18 at 8:52
    
example here that after running a complex query for the first time it took 23 seconds, using SQL_CACHE and SQL_NO_CACHE make no difference, the next running of the query took less then a second. –  ufk Mar 18 at 8:56
    
i read that OS and disk cache may also impact performance. but i can't believe that's the cause of the query execution time to be x23 faster –  ufk Mar 18 at 9:01

1 Answer 1

What you are really looking for is to have query cache misses close to 100%. I think I have what looking for. On July 09, 2011, I answered this post in the DBA StackExchange : Testing Query Speed.

Here is that answer:

You may want to impose a stress test environment to get query results to be as real time as possible. For example, the MyISAM Key Buffer (size governed by key_buffer_size) by default is 8MB, and the minimum value is 8 (that's right, 8 bytes). It is responsible for holding index pages from .MYI files. Set this value to 8 and every keyed lookup in MyISAM must be read over and over again.

This would also work in prinicple with InnoDB. The default InnoDB Buffer Pool Size (governed by innodb_buffer_pool_size) is 128MB and minimum is 1MB (in MySQL 5.5). It is responsible for holding data and index pages from .ibd and/or ibdata1 files. Set this value to 1M and every keyed lookup in InnoDB (which always includes an additional lookup in the clustered row index (gen_clust_index)) must be read over and over again.

For added stress, set the query_cache_type to 0 to force queries not to be cached.

Just add those three(3) minimum values into /etc/my.cnf

[mysqld]
innodb_buffer_pool_size=1M
key_buffer_size=8
query_cache_type=0

and restart MySQL.

Doing this should make all queries perform at its bare minimum best (or worst) every time.

Give it a Try !!!

Well, don't just sit there staring at the monitor...

Give it a Try !!!

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