… can be applied. Shard-Query works only on sets Shard-Query takes relational algebra to …which speaks SQL, but right now only MySQL storage nodes are supported. Amdahl’s …query with aggregation, a JOIN, and a WHERE clause that uses an IN clause: — INPUT SQL: select origin_airport_id, count…
Post: Shard-Query adds parallelism to queries
November 15, 2010 By 18 Comments
… of queries tests the most basic aggregation (count(*)) on a range of records. This table is partitioned by month which means that MySQL can… one query, it runs many smaller queries each requesting significantly less data. On the other hand, MySQL 5.5.7 does not do this on… involved the next four queries on Vadim’s list. The purpose of this test is to demonstrate that Shard-Query works with GROUP…
Post: Using delayed JOIN to optimize count(*) and LIMIT queries
April 6, 2007 By 22 Comments
…need to be joined to get query result. If you’re executing count(*) queries for such result sets MySQL will perform the join … +———-+ | count(*) | +———-+ | 7340032 | +———-+ 1 row in set (0.00 sec) mysql> select count(*) from fact where i select count(*) from fact left join dim on …
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
… timestamp=1325146286; select count(*) from auto_inc; Note that logging all queries in this fashion as opposed to the general query log, enables…. What it says though is that, if this query would run on a cold MySQL instance, then it would require reading nearly 40… run time, query ranked #1. The first row in the table above shows the Count of number of times this query was executed…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…MySQL manual, especially the option and variable reference table. But just as frequently, I want to look up blog posts on…
Post: Is it query which needs to be optimized ?
March 6, 2007 By 9 Comments
…MySQL Performance Forum as well as from our customers regarding query optimization… which had one thing in common – It is not query…COUNT(*) query can cause a lot of troubles. Imagine for example some sort of profile browsing at social networking site – SELECT COUNT… can be slow on large data sets …
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 141 Comments
…mysql> select count(pad) from large; +————+ | count(pad) | +————+ | 31457280 | +————+ 1 row in set (4 min 58.63 sec) mysql> select count…MySQL single query runs as single thread (with exeption of MySQL Cluster) and MySQL issues IO requests one by one for query… based on MySQL…
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
…requirements, the InnoDB versions are only available on 64 bit instances. MySQL will fail to start on a micro instance, simply decrease …exec time, the third parse time). $ echo “select count(*) from ontime_fact;” | ./run_query Array ( [count(*)] => 135125787 ) 1 rows returned (0.084244966506958s, 0…
Post: Advanced index analysis with mk-index-usage
November 11, 2010 By 2 Comments
…query log to my laptop, which is across the continent. I used a variation on MySQL…
Post: Innodb Table Locks
July 31, 2012 By 4 Comments
… mysql tables in use 2, locked 0 MySQL thread id 53038, OS thread handle 0x7ff759b22700, query id 3918786 localhost root Sending data select count… lock to “no lock” hence eliminating conflicts on MySQL level table locks for most queries. Summary: MySQL Table level locks and Innodb Table Level…
