Search Results for: mysql explain extended extra

A case for MariaDB’s Hash Joins

MariaDB 5.3/5.5 has introduced a new join type “Hash Joins” which is an implementation of a Classic Block-based Hash Join Algorithm. In this post we will see what the Hash Join is, how it works …

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Identifying the load with the help of pt-query-digest and Percona Server

Overview Profiling, analyzing and then fixing queries is likely the most oft-repeated part of a job of a DBA and one that keeps evolving, as new features are added to the application new queries pop …

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Emulating global transaction ID with pt-heartbeat

Global transaction IDs are being considered for a future version of MySQL. A global transaction ID lets you determine a server’s replication position reliably, among other benefits. This is great when you need to switch …

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A workaround for the performance problems of TEMPTABLE views

MySQL supports two different algorithms for views: the MERGE algorithm and the TEMPTABLE algorithm. These two algorithms differ greatly. A view which uses the MERGE algorithm can merge filter conditions into the view query itself. …

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InnoDB: look after fragmentation

One problem made me puzzled for couple hours, but it was really interesting to figure out what’s going on. So let me introduce problem at first. The table is

Table has 11864696 rows and …

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Another look at improving TPC-H-like queries – Q17

Summary: An alternate approach, offered in response to our original post, provides excellent improvements for smaller databases, but clustered indexes offer better performance as database size increases. (This posting is by Dave.) Jay Pipes suggested …

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Improving TPC-H-like queries – Q17

Executive Summary: A query like TPC-H Query 17 can be sped up by large factors by using straight_joins and clustering indexes. (This entry posted by Dave.) In a previous post, we wrote about queries like …

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JOIN Performance & Charsets

We have written before about the importance of using numeric types as keys, but maybe you’ve inherited a schema that you can’t change or have chosen string types as keys for a specific reason. Either …

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