As you might know while running GROUP BY and some other kinds of queries MySQL needs to create temporary tables, which can be created in memory, using MEMORY storage engine or can be created on disk as MYISAM tables. Which one will be used depends on the allowed tmp_table_size and also by […]Read more
I start to see applications being built utilizing VIEWs functionality which appeared in MySQL 5.0 and quite frequently VIEWs are used to help in writing the queries – to keep queries simple without really thinking how it affects server performance.
Even worse than that – looking at the short table which just gets single row […]
Recently we were puzzled by question how query_cache works with column level privileges. The question was appeared as we discovered function query_cache_send_result_to_client is called before real parsing of query, so at the moment of execution the query_cache is not able to know which columns are accessed.
Looking into source code I found out that in […]
Working on large upgrade of MySQL 4.1 running Innodb to MySQL 5.0 and doing oprofile analyzes we found very interesting issue of buf_get_latched_pages_number being responsible for most CPU usage. It did not look right.
The close look revealed this is the function which is used to compute number of latched pages […]
It is true you might be better of being unaware about problems, because in this case you might not run into them 🙂
Just couple of days ago Kaj Arno told me there are issues reported with SHOW PROFILE patch available in latest MySQL Community Edition and I’ve been troubleshooting customer affected by one of […]