Emergency

Search Results for: SQL_NO_CACHE

Query Profiling with MySQL: Bypassing caches

Quite frequently I run into question like this “I’m using SQL_NO_CACHE but my query is still much faster second time I run it, why is that ? The answer to this question is simple – …

Read More
 

To SQL_CALC_FOUND_ROWS or not to SQL_CALC_FOUND_ROWS?

When we optimize clients’ SQL queries I pretty often see a queries with SQL_CALC_FOUND_ROWS option used. Many people think, that it is faster to use this option than run two separate queries: one – to …

Read More
 

Getting real life query speeds with MySQL

To check for query performance improvements followed indexing/query changes or MySQL configuration changes our customers often decide to run the query and see if there is any significant improvement. Leaving aside question of checking single …

Read More
 

MySQL: Followup on UNION for query optimization, Query profiling

Few days ago I wrote an article about using UNION to implement loose index scan. First I should mention double IN also works same way so you do not have to use the union. So …

Read More
 

Using UNION to implement loose index scan in MySQL

One little known fact about MySQL Indexing, however very important for successfull MySQL Performance Optimization is understanding when exactly MySQL is going to use index and how it is going to do them. So if …

Read More
 

Cache Performance Comparison

Jay Pipes continues cache experiements and has compared performance of MySQL Query Cache and File Cache. Jay uses Apache Benchmark to compare full full stack, cached or not which is realistic but could draw missleading …

Read More
 

MySQL Query Cache

MySQL has a great feature called “Query Cache” which is quite helpful for MySQL Performance optimization tasks but there are number of things you need to know. First let me clarify what MySQL Query Cache …

Read More
 

Are larger buffers always better ?

Sometimes I see people thinking about buffers as “larger is always better” so if “large” MySQL sample configuration is designed for 2GB and they happen to have 16, they would simply multiply all/most values by …

Read More