MySQL

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MySQL

Would You Like Some Transactions With That Table?

Oct 29, 2009 www.brianhitchcock.net

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What Is MySQL?

Most popular open source RDBMSOpen source means 'free'

Really? No cost at all?Widely used

Sabre – airline reservationsGoogleLinkedIn

What does Oracle DBA need to know?Many differences...


Why Should I Care?

I'm an Oracle DBAMySQL means nothing to meIt isn't a 'real' RDBMS

Why should I learn about MySQL?MySQL is being used by real businessesCan't hurt your employabilityMany jobs expect DBA to know multiple RDBMS

Why not learn one that is widely used? And it's free – you can download and install right now!


Oracle DBA Perspective

What will we look at?InstallingStart/stopHow database/tables storedBackupsTransactions

Storage engines


My Message

Compare MySQL to OracleNot to be critical of MySQLNot to praise OracleMake Oracle DBAs aware

How much we assume about RDBMS Because Oracle does things a certain way

MySQL is very different Assuming it is like Oracle can cause serious problems

Does your business understand the differences? The cost of being 'free'?


MySQL Versions

MySQL EnterpriseHave to buy support

MySQL Community EditionThe 'free' version

MySQL Community Edition Preview ReleaseAvailable for downloadReady for prime time?

Oracle doesn't offer 12g for trial download...


MySQL Versions


MySQL – Where Did It Come From?

Used to store web site logsTransactions

What's that?If we lose some records

So what?Supported by an individual

Do your own thingRecovery

Not to worry, plenty more web logs every day


Some Differences – MySQL/OracleOracle

Database Schema

a group of database objects Database user

Maps to a database schemaMySQL

Server Databases

Group of database objects Users don't map to database


Some Differences – MySQL/OracleStorage enginesTransaction supportPerformanceHot backupBinary logging and recoveryTable lockingCorruptionMisc.


Storage Engines

MySQL gives you a choiceOracle, all transactional all the time (OATATT)

MySQL storage enginesMyISAM (IBM, Indexed Sequential Access Method)

Very fast readInnoDB

Transactional, like Oracle Separate software, owned by Oracle

Many others See next chart


Storage Engines


InnoDB Storage Engine

Imagine mixingMyISAM, InnoDB tables in a statementWhat does 'transactional' mean?What does “recovery” mean?


CSV Storage Engine

CSV storage engineStores data in text filesUsing comma-separated format


Blackhole Storage Engine

My favorite

This is where we store all the data relating to the Raiders andtheir 'Commitment to Excellence'


Yeah, But...

No problemI'll just make all the tables InnoDB

Cool, butMySQL catalog (system?) tables are MyISAMCan't change themTable storage engine can be changed at any time

Privileged users No one should do this, but...stuff happens

Create table syntax Supports overriding default storage engine


Transaction Support

MyISAMDefault table typeTable type of system databasesDoes not support transactionsExample

Writing to MyISAM tables and server crashes Who know what was and wasn't written to tables No recovery


Performance

Many large MySQL servers in usePerformance must be good

or good enough for 'free'Optimizer

Different storage enginesHow to optimize statement that has

MyISAM tables InnoDB tables

Does it support all storage engines you are using?


Hot BackupMySQL does not have this

Backup option #1 Shutdown server, copy all files, startup server

Backup option #2 Lock all tables Dump all data to a dump file

Dump file is set of SQL to recreate databaseVery slow to recover

Backup option #3 Buy hot backup software product

Not free


Binary Logging and Recovery

MySQLDefault, no loggingYou can configure binary loggingThree formats

Statement-based Row-based Mixed

Binary log filenames have format binlog.000001, binlog.000002, etc. You must apply them in correct order


MySQL Binary Logs

MySQL does not have any way of knowing when replaying the binary logs which statements need to be executed and which are already committed.

Oracle DBA doesn't worry about thisOracle checks and tells you which archived redo

log is needed nextOracle won't allow archived redo logs to be applied

out of order


Binary Logging Formats


Binary Log Issues


Table Locking

MyISAM storage engineDoes not support row level locking

Table locksPerformance?

InnoDB storage engineSupports row level locking


CorruptionOracle

I have rarely seen any casesBut all tables support transactions

MySQLWhat does it mean to rollback

When different storage engines involved Some support transactions, some don't Some tables will be rolled back

Others won'tIs this corruption?


MySQL Corruption Issues

Good readDiscusses corruption issues in MySQL enginesI'm not saying this happens often

But you need to be aware of these issues Another difference from Oracle

Different storage engines, different corruption mechanisms

http://www.mysqlperformanceblog.com/2006/07/30/mysql-crash-recovery/


MySQL IssuesMisc

Referential Integrity Some storage engines support

Triggers Row-level, not statement-level

Directload Not supported

Parallel Query Not supported


MySQL Issues

White PaperCompares MySQL to PostgreSQL

PostgreSQL, another open source RDBMS More like Oracle than MySQL

Discusses issues with MySQL I'm not endorsing PostgreSQL But the whitepaper is very good

Google PostgreSQL vs. MySQL A Comparison of Enterprise

Suitability


MySQL Table Storage

MyISAMEach table has three files

<filename>.frm – Data dictonary information <filename>.MYD – table data <filename>.MYI – table indexes

InnoDBData and indexes in a tablespaces

Made up of one or more datafiles Sound familiar?


Documentation Online


Talk Is Cheap

A little less conversationA little more action

Download and install MySQL to your laptop nowSlides show the steps

WindowsYou will have a fully functional MySQL server

Start learning right now


Install MySQL – Windows

Windows Vista6.0 Service Pack 1Screenshots shown

Windows XPProfessional Version 5.1Same stepsVery minor differences in what you see


Downloads?


Enterprise Version


Community Version


Windows Downloads


Windows Installation



Uncheck



Check



mysql


Accessing MySQL Windows

Click StartProgramsMySQLMySQL Server 5.1MySQL Command Line Client

Right-clickSend to

Desktop (Create Shortcut)Double-click desktop icon

MySQL Command Line Client


Accessing MySQL Windows

mysql

Shortcut created at installation


mysql client utility

Similar to SQL*Plus


Now What?Stop, start MySQL serverWhat databases are available

show databases;Set default database

use <dbname>What tables are in the database

show tables;


Windows Vista

Stop/StartServices

Start Settings Control Panel System and Maintenance Administrative Tools

Services Scroll down to MySQL, highlight Upper left, options for Stop, Pause, Restart If MySQL is down, option to Start


Windows XPStop/Start

Command line net stop mysql, net start mysql

Services Start Control Panel Administrative Tools Services

Services windowScroll down to MySQL, highlightUpper left, options for Stop, Pause, Restart

If MySQL is down, option to Start


System Databases

INFORMATION_SCHEMACatalog database

MYSQL databaseUser and privilege information

TESTFor you to play in...

These databases are created at installation


MySQL Server ConfigurationControlled by 'option' file(s)

Similar to Oracle pfile or spfileSHOW VARIABLES

See current valuesStandard location(s)

Search orderOne of the most common problems

Persons don't know where these files areMake changes that don't take affectCan't find the file or files


Option File(s)MySQL searches multiple locations

Uses most recent value of each parameterHow to know all files being scanned by MySQL?

mysql –help

Note: dash dash help


Option File


MySQL Filesystem LayoutFrom option file (my.ini)

basedir Where software is stored

datadir Where table data is stored


MySQL basedir


MySQL basedir/bin


MySQL datadir


MySQL Log Files

General Query LogAll client requests

Binary LogStatements that modify data

Slow Query LogStatements that take longer than 10 seconds

Error LogServer messages


MySQL Log Files

Find log file locations


Summary

MySQL is 'free'May need other products to make it work for you

Hot backup for exampleMySQL is widely usedMySQL is very different from Oracle

DBA tasks and issues will be differentMySQL is not better or worse than Oracle

Just very different


The End?

You now have a MySQL server installedNo excuses

Learn it, live it, love itUpdate your resume

Next?Multiple MySQL servers on same machineReplicationetc.

MySQL

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