… first table participating in the joins are read, and then for each of these rows an index lookup is performed on the second table. This… join condition and then a hash table lookup is performed, on the hash table we created earlier. This step is known as probe step. This join… quite large as compared to MySQL 5.6 and that is ‘Handler_mrr_init’. Is it because of this that the query on…
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
… the following query executed on the InnoDB table: SELECT non_key_column… If the buffer size is large enough only a single range…performing the benchmark on IO bound workload, mentioned above. Counter Name MySQL 5.5 MySQL 5.6 MySQL…post which will be on Block Access Join Algorithms. Conclusion There is…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 139 Comments
… perform over 300.000 of random lookups per second from single thread depending on system and table structure. Now if you data fully on… have star join with dimention tables being small it would not slow things down too much. On other hand join of few large tables, which is completely disk bound can be very slow. One of the reasons elevating this problem in MySQL…
Post: High-Performance Click Analysis with MySQL
December 22, 2008 By 13 Comments
… joins on large data sets are very expensive. If MySQL supported sort-merge or hash joins,… on huge tables, it lets you scan portions of a table instead of the whole table …MySQL doesn’t tend to perform well on a data warehousing workload. The nested-loop joins are not all that fast on big joins…
Post: Side load may massively impact your MySQL Performance
November 13, 2011 By 7 Comments
…seconds. Yes you get it right. Performance of sysbench OLTP on small table drops more than 150 times … innodb_sys_tables as t inner join innodb_sys_indexes as i using(table_id) inner join innodb_…in default configuration MySQL has buffer pool which can be easily washed away by large table scans or …
Post: Is your MySQL Application having Busy IO by Oracle Measures ?
January 8, 2012 By 1 Comment
…be exceptional for traditional MySQL as MySQL optimizer with its nested loops joins does not favor… can get a lot better performance with multiple MySQL instances on powerful storage. When you… large table and data sizes in MySQL can be painful, lacking online operations to alter table, …
Post: When Does InnoDB Update Table Statistics? (And When It Can Bite)
October 6, 2011 By 5 Comments
…table statistics is used for JOIN optimizations and helping the MySQL optimizer choose the appropriate index for a query. If a table…perform the updates aside from the first opening of the table or manually running ANALYZE TABLE on… [FULL] TABLES or SHOW TABLE STATUS on many a large tables, this can …
Post: ORDER BY ... LIMIT Performance Optimization
September 1, 2006 By 93 Comments
… with LIMIT is often the cause of MySQL Performance problems. Here is what you need to… what if you have application which can perform search on many different columns, with worse then …use index to do ORDER BY with JOIN MySQL still will not be able to use… about ORDER BY without limit and large tables…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…Performance_schema_rwlock_classes_lostblogpercona.commanual Performance_schema_rwlock_instances_lostblogpercona.commanual Performance_schema_table_handles_lostblogpercona.commanual Performance_schema_table_instances_lostblogpercona.commanual Performance…
Post: Data mart or data warehouse?
July 15, 2010 By 13 Comments
…perform better on a star schema than on a snowflake or fully normalized schema at data warehouse volumes. This is in large…tables and materialized views. These features make working with a star schema much easier than it may be on MySQL…
