…: OLTP_RO and POINT_SELECT from the latest sysbench-0.5 dataset consists of 4 sysbench tables(50M rows each) ~50G data… below) there are spikes for it that may be caused by some contention in the lib. All variations of glibc that are based on…, results are very similar to lockless/jemalloc-3.0/tcmalloc. For POINT_SELECT test with increasing concurrency we have two allocators that handle load…
Post: Shard-Query turbo charges Infobright community edition (ICE)
May 6, 2011 By 23 Comments
…/or multiple cores. This is similar to the divide and conquer approach that Hive takes in combination with Hadoop… there are only 29 air carriers in the table: mysql> select count(*), count(distinct UniqueCarrier) from dim_flightG *************************** 1. row *************************** count…
Post: Multi Column indexes vs Index Merge
September 19, 2009 By 31 Comments
…there are no more matching. The RANGES such as AGE BETWEEN 18 AND 20 work similar way… internally storage engine can use that value to lookup the full row data corresponding to the…rows” is very wrong here. This happens because Optimizer assumes columns i1 and i2 are independent estimating selectivity…
Post: Using any general purpose computer as a special purpose SIMD computer
May 16, 2011 By 5 Comments
…similar to other technologies on the market today. However, the scaling features of Shard-Query are…rows returned (0.87930011749268s, 0.87229418754578s, 0.0070059299468994s) Why six degrees of parallelism? Because that is how many physical cores are… are combined with this. — AGGREGATION SQL: SELECT …
Post: Full table scan vs full index scan performance
November 23, 2012 By 15 Comments
…That‘s why when execution plans look similar…selecting all the fields: mysql> explain SELECT first_name FROM employees ORDER BY first_name\G *************************** 1. row *************************** id: 1 select…
Post: Eventual Consistency in MySQL
November 18, 2011 By 8 Comments
… empty, then there are no orphaned rows. But there are probably hundreds of…are non-null. From that information, we can generate an exclusion-join query for each foreign key relationship: mysql> SELECT CONCAT( ‘SELECT… relationship. That‘s okay, we can create a conventional table with similar …
Post: Recovering Innodb table Corruption
July 4, 2008 By 22 Comments
…rows affected (0.03 sec) mysql> insert into test2 select * from test; Query OK, 229376 rows…failed | +———–+———-+———-+———————————-+ 2 rows in set, 2 warnings (0.09 sec) That was… you – they are helpful in …row between 200 and 300 and we can do bunch of similar…
Post: Knowing what pt-online-schema-change will do
November 1, 2012 By 1 Comment
… create those triggers by executing those SQL statements. Similarly, the tool does not copy rows because this is a dry run, but… chosen rather than the PRIMARY key. That signals that the tool has done something wrong. Are all columns selected? Hopefully the tool will never make such a grievous mistake, but on never knows. Are the columns…
Post: Analyzing air traffic performance with InfoBright and MonetDB
October 2, 2009 By 50 Comments
… not like scanning wide range of rows, the slowness here is similar to Q0. -Q8: As final I…Q9: And prove that MonetDB does not like to scan many records, there is query select year,count(*) as… do not have indexes like InfoBright, but results are impressive. On drawbacks – the command line is weak (…
Post: Percona XtraDB Cluster: Multi-node writing and Unexpected deadlocks
August 17, 2012 By 17 Comments
…checking for circular dependencies, but that would be much more complicated in…row: node1 mysql> set autocommit=off; Query OK, 0 rows affected (0.00 sec) node1 mysql> select…with/around this problem? Here are some ideas from simplest to …with an HAproxy configuration or similar so if your main writer …
