… the database to do row lookups by multiple columns of varchars is likely. Don’t… using multiple databases to group tables by certain logic, such as > you do with directories to group files… frequently told by people with traditional database background. > Things are different with MySQL. Good design …
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
…than the join_buffer_size, then multiple hash tables would be created. …with its EXPLAIN output as returned by MySQL 5.5 is as follows: SELECT…> ’1996-05-01′ GROUP BY o_orderkey ORDER BY num_items DESC LIMIT 10; …
Post: High availability for MySQL on Amazon EC2 – Part 2 - Setting up the initial instances
June 29, 2010 By 9 Comments
…:~$ ec2-add-group hamysql -d ‘nodes for HA MySQL solution’ GROUP hamysql nodes for HA MySQL solution From now… one line the parameters I need separated by a delimiter. yves@yves-laptop:~$ cat filtre_instances… manager MySQL, just the host running it. I’ll also skip the raid configuration of multiple …
Comment: A common problem when optimizing COUNT()
September 21, 2008 By 19 Comments
… support the count’ing on multiple columns. I was smoking crack with the comment about ONLY_FULL_GROUP_BY . I need to stay… only_full_group_by mode can be attributed to many MySQL users not understanding what is going on when they type GROUP BY. I think that ONLY_FULL_GROUP_BY was a checkbox that was checked so that MySQL might allow some…
Post: Sphinx 0.9.8 is released just in time for OSCON 2008
July 20, 2008 By 2 Comments
… to multiple cores and multiple nodes, with close to linear scalability. Because of this we included Sphinx chapter in High Performance MySQL book… 7.5 seconds using MySQL with best covering index (so no temporary table or sorting is needed for group by). Note that with Sphinx you can easily run the process on multiple cores/multiple nodes. Anyways I’m…
Post: Missing Data - rows used to generate result set
July 20, 2008 By 15 Comments
… fraction of queries. If you’re joining multiple tables or if you have GROUP BY query the number of rows which need to… optimizing this query. For example: SELECT GENDER, COUNT(*) FROM PEOPLE GROUP BY GENDER This query will return only couple of rows but… (SELECT COUNTRY,COUNT(*) FROM PEOPLE GROUP BY COUNTRY) C WHERE COUNTRY=’USA’ As of MySQL 5.0 MySQL will materialize the subquery in the…
Post: PHP Large result sets and summary tables.
July 6, 2007 By 8 Comments
…creating of summary tables which was done by executing some huge group by query, doing some stuff with … space) like crazy. Why ? Because by default mysql_query uses mysql_store_result C library call and … flushes, ie with multiple value INSERTs etc. This can be fixed by increasing net_write_timeout …
Post: Intro to OLAP
July 12, 2010 By 10 Comments
…. Comparing the performance of OLAP with and without aggregation over multiple MySQL storage engines at various data scales. What is BI? Chances… data broken down into different groups. A typical OLAP analysis might show “sale total, by year, by sales rep, by product category”. OLAP analysis…
Post: Goal driven performance optimization
December 22, 2008 By Leave a Comment
…page_type=’search’ and wtime>1 group by h; +——+———-+—————–+——————+ | h | count(*) | avg(wtime) | sphinx_ratio | +——+———-+—————–+——————+ | …mutliple components (like sphinx and MySQL) or multiple MySQL Servers because in these cases you…
Post: Jeremy Cole on MySQL Replication
May 27, 2006 By 12 Comments
… MySQL 5.0 – if you enabled Binary log with MySQL 5.0 you loose group commit which can dramatically increase commit rate for multiple user load. See this post by Vadim… multiple disks they will not be used effectively as replication SQL thread will typically submit IO requests to the disk one by…
