June 18, 2013

Post: MySQL Query Cache

July 27, 2006 By 70 Comments

…get data in chunks so it is even harder to implement. Might not work with transactions – Different transactions may see different states of the database…of usable memory – Queries are constantly being invalidated from query cache by table updates, this means number of queries in…

Filed Under: Insight for DBAs Tagged With:

Post: Shard-Query adds parallelism to queries

November 15, 2010 By 18 Comments

…of a small number of concurrent queries (or only one) to demonstrate how much improvement could be made to…of those are not open source. In the future, Shard-Query can be extended to other database…

Filed Under: Insight for Developers, MySQL Tagged With: , , , ,

Post: Why MySQL could be slow with large tables ?

June 9, 2006 By 141 Comments

…to several tables or perform complex queries finding relationships between objects. Normalized structure and a lot of joins is right way to design your database…number of CPUs will not help. Sometimes it is good idea to manually split query into several, run in…

Filed Under: Insight for DBAs Tagged With: ,

Post: Recovery beyond data restore

August 2, 2008 By 11 Comments

…SQL_LOG_BIN=0 set for session. If the large portion of data trashed you may need to recover full database…to be accounted for for in the process of replication. It is also worth to note beyond these 3 main recovery scenarios there are number of…

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Post: A common problem when optimizing COUNT()

September 20, 2008 By 19 Comments

…to do. You can’t fully optimize a query unless you know how to consider alternative ways to…table; If you know your SQL well, you know COUNT() has two meanings. 1) count the number of rows 2) count the number of…

Filed Under: Insight for Developers Tagged With: ,

Post: Speeding up GROUP BY if you want aproximate results

March 7, 2008 By 24 Comments

… I wanted to count how many hits come to the pages which get more than couple of visits per day. We had SQL logs in the database so… quite slow. Of course it would be possible to allocate more memory to the temporary table or switch to filesort method and get result faster. I… to share which I use a lot when I want to analyze data distribution but table is to large is to just limit it to first number of…

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Post: Updated msl (microslow) patch, installation walk-through!

April 20, 2008 By 17 Comments

…database binary should be now available in sql subdirectory: (garfield:~/work/mysql-5.0.51a) % ls -l sql…to get the full sessions logged while doing it only for every n-th of them thus limiting the number of writes to…

Filed Under: Percona Software Tagged With:

Post: Filtered MySQL Replication

November 7, 2007 By 8 Comments

…table options also have some issues they are much safer than database based counterparts. In…to the group of slaves. If you have several group of slaves which need different data sets replicated to them – you can use number of…

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Post: Read/Write Splitting with PHP Webinar Questions Followup

January 23, 2013 By 4 Comments

…to scale out to multiple database instances. Q: Isn’t opening multiple database connections to the master and then subsequently potentially a number of “unsafe” slaves going to…

Filed Under: Events and Announcements, Insight for Developers, MySQL Tagged With: , ,

Post: Sphinx search performance optimization: multi-threaded search

January 16, 2013 By 10 Comments

…to its single-threaded nature. This is however easy to check – look at your Sphinx query log and look at the number of…to be ranges by using a helper table in MySQL to define those ranges, mixing it with sql_query_range or something else, depending on how…

Filed Under: MySQL Tagged With: , , ,
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