…MySQL does have its limitations, it reports only a subset of stats, however if you compare that to Percona server, it… SET timestamp=1325146286; select count(*) from auto_inc…means it accesses these pages in memory. What it says though is that, if this query would run on a cold MySQL instance, then it…
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
Post: MySQL Query Cache WhiteSpace and comments
March 20, 2008 By 9 Comments
…mysql> select count(*) from fact where val like “%c%”; +———-+ | count(*) | +———-+ | 0 | +———-+ 1 row in set (8.79 sec) mysql> select count(*) from fact where val like “%c%”; +———-+ | count…
Post: MySQL 5.6 vs MySQL 5.5 and the Star Schema Benchmark
March 11, 2013 By 7 Comments
…time. It does …BP, this means the FS …from MySQL 5.5.30, which performs significantly better on the repeat warm runs. Just to be sure it…practice it is problematic. What…mysql> select sq.*, pages / (@@innodb_buffer_pool_size / 16384) * 100 pct_buffer_pool from ( select table_name, index_name, count…
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
…SELECT non_key_column FROM tbl WHERE pk_column=val As you can see that the values returned from…It does not actually mean that queries with MRR are performing badly. The interesting thing is that though both MariaDB and MySQL…
Post: Joining on range? Wrong!
May 17, 2010 By 10 Comments
…What does EXPLAIN have to say about this? *************************** 1. row *************************** id: 1 select…) table, it works as expected: EXPLAIN SELECT COUNT(1) FROM items_… the full index length. It means both index columns …. #8569, #19548). Some replies from MySQL indicate this may …
Post: Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact
March 12, 2012 By 12 Comments
… in preparation for the talk comparing the optimizer enhancements in MySQL 5.6 and MariaDB 5.5. We are taking a… (ICP). Its available in both MySQL 5.6 and MariaDB 5.5 Now let’s take a look briefly at what this enhancement actually is, and what is it…
Post: How FLUSH TABLES WITH READ LOCK works with Innodb Tables
March 23, 2012 By 20 Comments
…what the problem is. As of MySQL 5.5 FLUSH TABLES WITH READ LOCK does not work as optimally as you could think it… | dumptest | Query | 324 | Sending data | select count(*) from A,B | 0 | 0 | 2359297 | | …means single run away select can effectively cause downtime if you use backup solution which does…
Post: Shard-Query adds parallelism to queries
November 15, 2010 By 18 Comments
…means that if MySQL could fully utilize all cores for my workload, then this test would be CPU bound. What…SELECT count(*) from ontime.ontime where FlightDate between ’1988-01-01′ and ’1988-12-31′; Q2 – SELECT DayOfWeek, count(*) AS c FROM…
Post: ANALYZE: MyISAM vs Innodb
September 3, 2008 By 9 Comments
… basic information means it does not … off, so what ? What really …it with data with following true cardinality: mysql> select count(distinct c) from antest; +——————-+ | count(distinct c) | +——————-+ | 101 | +——————-+ 1 row in set (0.36 sec) mysql> select count…
Post: Analyzing air traffic performance with InfoBright and MonetDB
October 2, 2009 By 50 Comments
…load statement is: mysql -S /tmp/mysql-ib.sock -e …It seems it does not use any compression, and it‘s bigger than original data. LucidDB Here it… SELECT count(*) FROM ontime;. Both InforBritgh and MonetDB executes it … I do not know what is the magic behind… smaller rate 1:10 means you can compress 1TB…
