Following on from my fun post on Where are they now: MySQL Storage Engines, I thought I’d cover the few storage engines that are really just interfaces to a collection of things. In this post, I’m talking about MERGE.

The MERGE engine was basically a multiplexer down to a number of MyISAM tables. They all had to be the same, there was no parallel query execution and it saw fairly limited use. One of the main benefits was that then you could actually put more rows in a MyISAM table than your “files up to 2/4GB” file system allowed. With the advent of partitioning, this really should have instantly gone away

mysql> create table nye (`event_id` int not null auto_increment,`edate` year(4) not null, description varchar(200), 

    -> primary key(`event_id`,`edate`)) 

    -> partition by range( edate ) (

    -> partition p2010 VALUES LESS THAN (2011), 

    -> partition p2011 VALUES LESS THAN (2012), 

    -> partition p2012 VALUES LESS THAN (2013) );
Query OK, 0 rows affected (0.04 sec)

mysql> INSERT INTO nye(edate,description) VALUES('2010','twenty ten'); 

Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO nye(edate,description)

common_schema 1.2 is released! This version comes shortly after 1.1, yet contains quite a few interesting goodies:

• Account blocking
• Security audit
• RANGE partition management
• Slave status
• Better blocking and idle transaction management
• QueryScript goodies:
  • echo, report
  • while-otherwise statement; foreach-otherwise statement
  • Better variable scope handling
  • Complete support for variable expansion
  • Transaction support within QueryScript
• More summary info and SQL statements in processlist-related views

A closer look at these follows:

Account blocking

A new view called

If you use RANGE (or RANGE COLUMNS) partitioning, and in particular when partitioning by date/time, then your are subject to the following questions: how and when do you create the "next" partition? How and when do you drop your older partitions?

Many people use in-house scripting to do that, and Giuseppe Maxia wrote Partition Helper. But I would like to take you one step forward, and provide with a query (based on views) which automagically understands which new partition you want to create, and provides you with the statement to do so. It looks somewhat like this (a demo follows later on):

mysql> SELECT * FROM sql_range_partitions \G
*************************** 1. row

While looking at partitioning I recently made a mistake which I guess can happen to others. Often this is due to not fully reading the documentation or scanning it too quickly and misunderstanding what’s being said.

So this post is to complain about the MySQL partitioning syntax and to warn others who may easily make the same mistake without realising.

First we probably need to ask why we are partitioning a table in the first place. The main reasons for this are I think:

• to improve query performance
• to reduce individual .ibd file sizes for large tables (if using innodb_file_per_table)

In my case I wanted to do both. I had a several tables which store a large number of rows (batches of data) based on an incremental batch number. One of these tables was around 40 GB and had about 500,000,000 rows in it.  When processing

CREATE TABLE message (
 message_id BINGINT UNSIGNED PRIMARY KEY,
 user_id INT UNSIGNED,
 body VARCHAR(255),
 ...
 created DATETIME,
 INDEX(user_id)
) ENGINE=InnoDB;

San Francisco, April 7th

Santa Clara, April 11, 12

• April 11, 9:00am

At Kscope this year, I attended a half day in-depth session entitled Data Warehousing Performance Best Practices, given by Maria Colgan of Oracle. My impression, which was confirmed by folks in the Oracle world, is that she knows her way around the Oracle optimizer.

See part 1 for the introduction and talking about power and hardware. This part will go over the 2nd “P”, partitioning. Learning about Oracle’s partitioning has gotten me more interested in how MySQL’s partitioning works, and

One common question I get is how to use partitioning instead of MERGE tables. The process I use involves using stored procedures to create and drop partitions. This article will go over the stored procedures I use; special thanks to Roland Bouman for taking a look and giving great feedback to optimize this process.

First, a simple table, not partitioned (yet):

use test;
DROP TABLE IF EXISTS my_part;
CREATE TABLE IF NOT EXISTS my_part (
  id int NOT NULL,
  creationDate datetime NOT NULL,
  PRIMARY KEY (id,creationDate)
) ENGINE=InnoDB;

In real, life there is more to the table than just id and creationDate. The most important part is that the partitioned field(s) need to be part of the primary key.

Now, add the partition definition. This can be done in the

select c2, 
       sum(s0.c1), 
       max(c1) 
 from t1 as s0 
 join t1 using (c1,c2) 
 where c2 = 98818 
 group by c2;

TO_DAYS() prunes two partitions instead of one

How it works

Overview

USE test;
DROP TABLE IF EXISTS users;

CREATE TABLE users (