# Custom Mysql queries slower than ActiveRecord in production

**URL:** <https://www.ruby-forum.com/t/custom-mysql-queries-slower-than-activerecord-in-production/135441>\
**Category:** Rails\
**Created:** [April 22, 2008, 8:05am UTC](https://www.ruby-forum.com/t/custom-mysql-queries-slower-than-activerecord-in-production/135441 "2008-04-22T08:05:55Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![fipa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/9e8a1a/32.png) [@fipa](https://www.ruby-forum.com/u/fipa)\
**Post date:** [April 22, 2008, 8:05am UTC](https://www.ruby-forum.com/t/custom-mysql-queries-slower-than-activerecord-in-production/135441/1 "2008-04-22T08:05:55Z")

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I have been working on optimizing the performance of a Rails app by  
rewriting the AR record methods into custom sql queries. What I did is  
that the result from the query is not instantiated as an object, which  
is supposed to be too time consuming.

Here are the performance difference between using default AR methods and  
its custom equivalent. The number of requests per second was read from  
the log file, it is not super accurate but gives a relative figure which  
is fine.

The first figure is the default AR method, the second one is the custom  
query.

In development mode:  
find(:all): 15 req/s -\> 30 req/s. Wow I get twice as much throughput.

In production mode:  
find(:all): 80 req/s -\> 60 req/s. Damn’it!

I don’t understand why in production mode, my custom sql query yields  
less performance than the AR methods.

What am I missing?

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<div class="post-metadata">

**Author:** ![fipa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/9e8a1a/32.png) [@fipa](https://www.ruby-forum.com/u/fipa)\
**Post date:** [April 22, 2008, 8:38am UTC](https://www.ruby-forum.com/t/custom-mysql-queries-slower-than-activerecord-in-production/135441/2 "2008-04-22T08:38:44Z")

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On Apr 21, 2008, at 11:05 PM, Fernando P. wrote:

> I don’t understand why in production mode, my custom sql query yields  
> less performance than the AR methods.

Are you, perchance, defeating AR query caching by writing the custom  
SQL?

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**Author:** ![fipa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/9e8a1a/32.png) [@fipa](https://www.ruby-forum.com/u/fipa)\
**Post date:** [April 22, 2008, 9:04am UTC](https://www.ruby-forum.com/t/custom-mysql-queries-slower-than-activerecord-in-production/135441/3 "2008-04-22T09:04:03Z")

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Hi Steve,

You nailed it! I completely forgot about query caching. I guess it might  
be turned off in production mode.

Therefore writing custom queries is only efficient for operations to the  
DB that will only be run once such as creating a new entry or retrieving  
data across many tables.

I have to learn exactly how query caching is implemented.

Thank’s a lot for pointing this out.