…column‘ which is a part of the secondary key tuple, a point primary key lookup is made against base table…to MySQL 5.5, and this does not make sense to me. Probably its due to a…to under a minute. The query time is reduced further when buffer size is set large…
Post: High-Performance Click Analysis with MySQL
December 22, 2008 By 13 Comments
…tables, and include columns to support these queries. But beware of denormalizing with character data; try to…s go back to the ad-by-day table. If you…to write a little more complex queries, but that’s often justified by a large reduction in table…is that MySQL doesn’t tend to perform well on a data …
Post: Shard-Query turbo charges Infobright community edition (ICE)
May 6, 2011 By 22 Comments
…a similar fashion, a final table `ontime_fact` is created by joining the newly constructed dimension table tables to the staging tables, omitting the dimension columns…to examine a large amount of data. Shard-Query includes a loader (loader.php) which can be used to either split a…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 17 Comments
…to set this value to a LARGE value (somewhat like 200) for additional throughput? HT: ha_innodb.cc in 5.1: static MYSQL…columns of a foreign key constraint need not form a primary key or a unique constraint: it is sufficient if the referenced columns form a…
Post: Shard-Query adds parallelism to queries
November 15, 2010 By 16 Comments
…to say that a typical OLAP workload features a low number of concurrent queries which each examine large amounts of data. Since a…table into months using the FlightDate column using the improved MySQL 5.5 partitioning options which work directly on columns without the need to use TO…
Post: How number of columns affects performance ?
September 28, 2009 By 10 Comments
… format table with many columns. But is it because of large number of columns …to MyISAM. The common workaround working with such wide tables is to use covering indexes. I added one to t99v1 table and repeated the query: mysql…Innodb is a lot slower and has behavior similar to Dynamic Row tables in …
Post: Multi Column indexes vs Index Merge
September 19, 2009 By 30 Comments
…to execute. now if we change it: If we disable index on the second column we get a full table scan: mysql…large performance difference between full table scan and access through the index, which seems to…
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
…to set it back to a value greater than 0, because otherwise you can have a really large…a cold MySQL…columns being accessed by the query. So a quick fix here could be to instead of selecting every column from all the tables…
Post: Hijacking Innodb Foreign Keys
January 2, 2012 By 2 Comments
…tables which are large enough it will range from inconvenient to not acceptable. As result you might have to resort to dirty solutions. Here is a…to be able to satisfy foreign key conditions (have column child table is referencing and have it of proper type and indexed): mysql…
Post: Dynamic row format for MEMORY tables
September 6, 2011 By 3 Comments
…tables can have BLOB and TEXT columns, and VARCHAR columns will not waste space due to implicit extension to…MySQL in 2008): The key columns must come before any non-key variable-length columns. For performance reasons, the key columns are stored in a…
