Comments on: MySQL Query Cache http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/ Everything about MySQL Performance Fri, 04 Jul 2008 15:15:52 +0000 http://wordpress.org/?v=2.5.1 By: Aijaz http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-322017 Aijaz Thu, 03 Jul 2008 06:31:24 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-322017 I have created a table which has 1 lakh of records but the problem is ..when m trying to perform a Query on this table ... it consists of 3-4 tables joins ... so it takes around 7-8 mins to fetch the data ... Then i tried to Built Index on few columns.... But when we Explain that Query ... thn also it shows ALL instead of the index type of any I have created a table which has 1 lakh of records but the problem is ..when m trying to perform a Query on this table … it consists of 3-4 tables joins … so it takes around 7-8 mins to fetch the data … Then i tried to Built Index on few columns…. But when we Explain that Query … thn also it shows ALL instead of the index type of any

]]> By: peter http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-297238 peter Sun, 11 May 2008 06:40:34 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-297238 nawab, Typically people would use either memcache or query cache. Invalidation is important part of being transparent - if you do not invalidate you get stale data from cache so it is not transparent for application any more - application needs to be aware it is getting the stale data. And what if it needs the most recent one ? Using memcache or other cache explicitly allows control over how invalidation works. nawab,

Typically people would use either memcache or query cache. Invalidation is important part of being transparent - if you do not invalidate you get stale data from cache so it is not transparent for application any more - application needs to be aware it is getting the stale data. And what if it needs the most recent one ?

Using memcache or other cache explicitly allows control over how invalidation works.

]]> By: nawab http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-297180 nawab Sat, 10 May 2008 16:25:16 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-297180 thanks for the informative article. i would like to know if there is some transparent query cache available for mysql that is not ACID safe. something to work with high update scenario, the cache is NOT dropped with every table change. memcached is one option, but it is not transparent, i.e., i need to modify in application every place where an expensive mysql query is being done. i would rather prefer a transparent way, e.g., something implemented as a wrapper over JDBC classes with local in-memory caching. or a set of APIs that first query the memcached/JCS/EHCache and if nothing is found, query the MySQL database. thanks thanks for the informative article.

i would like to know if there is some transparent query cache available for mysql that is not ACID safe. something to work with high update scenario, the cache is NOT dropped with every table change. memcached is one option, but it is not transparent, i.e., i need to modify in application every place where an expensive mysql query is being done. i would rather prefer a transparent way, e.g., something implemented as a wrapper over JDBC classes with local in-memory caching. or a set of APIs that first query the memcached/JCS/EHCache and if nothing is found, query the MySQL database.

thanks

]]> By: MySQL Query Cache WhiteSpace and comments | MySQL Performance Blog http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-254924 MySQL Query Cache WhiteSpace and comments | MySQL Performance Blog Thu, 20 Mar 2008 17:56:09 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-254924 [...] on my previous post on MySQL Query Cache Gerry pokes me as I'm all wrong and both comments and whitespace are fixed in [...] [...] on my previous post on MySQL Query Cache Gerry pokes me as I’m all wrong and both comments and whitespace are fixed in [...]

]]> By: Gerry http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-254833 Gerry Thu, 20 Mar 2008 08:27:11 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-254833 "AFAIR but comments are not" Hmmmm... as far as you remember.... but from where? Where would you have got this information? The second link I provided says that the comments/space issue was fixed in MySQL 5 “AFAIR but comments are not”

Hmmmm… as far as you remember…. but from where? Where would you have got this information?

The second link I provided says that the comments/space issue was fixed in MySQL 5

]]> By: peter http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-244690 peter Tue, 19 Feb 2008 18:31:26 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-244690 Gerry, At the point this article was written (about 1.5 years ago) the prepared statements did not work with query cache. Even now they are only supported in MySQL 5.1 which is still not production release. The problem with spaces was indeed partially fixed. Basic whitespace is fixed AFAIR but comments are not. Gerry,

At the point this article was written (about 1.5 years ago) the prepared statements did not work with query cache. Even now they are only supported in MySQL 5.1 which is still not production release.

The problem with spaces was indeed partially fixed. Basic whitespace is fixed AFAIR but comments are not.

]]> By: Gerry http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-244616 Gerry Tue, 19 Feb 2008 06:47:53 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-244616 Some of the information in this blog entry is out of date and thus incorrect: ie. > "Avoid comment (and space) in the start of the query - Query Cache does simple optimization to check if query can be cached. As I mentioned only SELECT queries are cached - so it looks at first letter of the query and if it is “S” it proceeds with query lookup in cache if not - skips it." I just wasted a couple of hours on this one only to realise that the statement was incorrect and based on a bug which has long since been fixed. Other things in this article are wrong too. For instance some prepared statements will in fact work. Check the manual for more accurate info on what will and won't work. And the Pro MySqL book that I have always documents issues such as this, but does not mention this problem and the same goes for the MySQL manual. I would have preferred if the author had specified where he was getting his info so I didn't have to waste so much time looking into this. This guy tested it: http://www.petefreitag.com/item/390.cfm This documents that the bug only exists in older 4.0 version of MySQL: http://books.google.com/books?id=iaCCQ13_zMIC&pg=PA80&lpg=PA80&dq=white+space+query+cache&source=web&ots=3ED_193Hn1&sig=Ctiy3T5zxWyJHuKnqBtHxuofm3Q Some of the information in this blog entry is out of date and thus incorrect:

ie.

> “Avoid comment (and space) in the start of the query - Query Cache does simple optimization to check if query can be cached. As I mentioned only SELECT queries are cached - so it looks at first letter of the query and if it is “S” it proceeds with query lookup in cache if not - skips it.”

I just wasted a couple of hours on this one only to realise that the statement was incorrect and based on a bug which has long since been fixed.

Other things in this article are wrong too. For instance some prepared statements will in fact work. Check the manual for more accurate info on what will and won’t work.

And the Pro MySqL book that I have always documents issues such as this, but does not mention this problem and the same goes for the MySQL manual. I would have preferred if the author had specified where he was getting his info so I didn’t have to waste so much time looking into this.

This guy tested it:
http://www.petefreitag.com/item/390.cfm

This documents that the bug only exists in older 4.0 version of MySQL:
http://books.google.com/books?id=iaCCQ13_zMIC&pg=PA80&lpg=PA80&dq=white+space+query+cache&source=web&ots=3ED_193Hn1&sig=Ctiy3T5zxWyJHuKnqBtHxuofm3Q

]]> By: Ibuildings Blog http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-236062 Ibuildings Blog Wed, 30 Jan 2008 13:00:49 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-236062 <strong>Different methods of caching</strong> Because we encounter PHP more and more in the enterprise market, the performance demands of websites we build are becoming ever more challenging. The usefulness of caching is often underestimated by developers (myself included). When using a lightweight f Different methods of caching

Because we encounter PHP more and more in the enterprise market, the performance demands of websites we build are becoming ever more challenging. The usefulness of caching is often underestimated by developers (myself included). When using a lightweight f

]]> By: McBOX » Blog Archive » Ways To Speed Up WordPress With Caching http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-225754 McBOX » Blog Archive » Ways To Speed Up WordPress With Caching Mon, 31 Dec 2007 00:00:43 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-225754 [...] Since WordPress uses MySQL, almost every page load results in various MySQL queries for logins, post content, categories and so on. It is very likely that this data didn’t change since the last request so we begin with enabling the cache within the MySQL server. Basically, all you need to to is to activate it in the my.cnf (or my.ini) MySQL configuration file with setting the query-cache-type variable to 1. The query-cache-size variable is the size of the query cache in MB, for example 20M. To change the MySQL configuration file, you’ll probably need root access which won’t be available on shared hosts. More info about query cache is available on techiecorner.com and the MySQL Performance blog. [...] [...] Since WordPress uses MySQL, almost every page load results in various MySQL queries for logins, post content, categories and so on. It is very likely that this data didn’t change since the last request so we begin with enabling the cache within the MySQL server. Basically, all you need to to is to activate it in the my.cnf (or my.ini) MySQL configuration file with setting the query-cache-type variable to 1. The query-cache-size variable is the size of the query cache in MB, for example 20M. To change the MySQL configuration file, you’ll probably need root access which won’t be available on shared hosts. More info about query cache is available on techiecorner.com and the MySQL Performance blog. [...]

]]> By: » MySQL query cache | PageTracer | Webmasters mashup http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-214935 » MySQL query cache | PageTracer | Webmasters mashup Sun, 09 Dec 2007 12:50:26 +0000 http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/#comment-214935 [...] Here you can find the great post about other limitations of the MySQL query cache and MySQL query cache efficiency. [...] [...] Here you can find the great post about other limitations of the MySQL query cache and MySQL query cache efficiency. [...]

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