July 31, 2014

On Character Sets and Disappearing Tables

The MySQL manual tells us that regardless of whether or not we use “SET FOREIGN_KEY_CHECKS=0″ before making schema changes, InnoDB will not allow a column referenced by a foreign key constraint to be modified in such a way that the foreign key will reference a column with a mismatched data type. For instance, if we […]

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 and for what types of queries would it be the right choice. I will show the results of executing benchmarks […]

Testing Samsung SSD SATA 256GB 830 – not all SSD created equal

I personally like PCIe based Flash, but from a pricing point our customers are looking for cheaper alternatives. SATA SSD is an options. There is many products based on MLC technology, and Intel 320 I would say is the most popular. I do not particularly like its write performance – I wrote about it before, […]

Joining many tables in MySQL – optimizer_search_depth

Working on customer case today I ran into interesting problem – query joining about 20 tables (thank you ORM by joining all tables connected with foreign keys just in case) which would take 5 seconds even though in the read less than 1000 rows and doing it completely in memory. The plan optimizer picked was […]

Shard-Query EC2 images available

Infobright and InnoDB AMI images are now available There are now demonstration AMI images for Shard-Query. Each image comes pre-loaded with the data used in the previous Shard-Query blog post. The data in the each image is split into 20 “shards”. This blog post will refer to an EC2 instances as a node from here […]

Moving Subtrees in Closure Table Hierarchies

Many software developers find they need to store hierarchical data, such as threaded comments, personnel org charts, or nested bill-of-materials. Sometimes it’s tricky to do this in SQL and still run efficient queries against the data. I’ll be presenting a webinar for Percona on February 28 at 9am PST. I’ll describe several solutions for storing […]

How well does your table fits in innodb buffer pool ?

Understanding how well your tables and indexes fit to buffer pool are often very helpful to understand why some queries are IO bound and others not – it may be because the tables and indexes they are accessing are not in cache, for example being washed away by other queries. MySQL Server does not provide […]

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. This has significant performance advantages over TEMPTABLE views. A view which uses the TEMPTABLE algorithm will have to compute the […]

How well do your tables fit in buffer pool

In XtraDB we have the table INNODB_BUFFER_POOL_PAGES_INDEX which shows which pages belong to which indexes in which tables. Using thing information and standard TABLES table we can see how well different tables fit in buffer pool.

You can also see in one of the cases the value shown is a bit over 100% – […]

XtraDB/InnoDB CPU bound benchmarks on 24cores server

One of our customers gave me a chance to run some benchmarks on 24-core (intel cpu based) server, and I could not miss it and ran few CPU-bound tasks there. The goal of benchmarks was investigation of InnoDB-plugin and XtraDB scalability in CPU-bound load.