MySQL Would You Like Transactions

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www.brianhitchcock.net

MySQL

Would You Like Some TransactionsWith That Table?


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www.brianhitchcock.netOct 29, 2009 Page 2

Slides Are Available


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What Is MySQL?

Most popular open source RDBMSOpen source means 'free'

Really? No cost at all?

Widely usedSabre airline reservationsGoogle

LinkedInWhat does Oracle DBA need to know?

Many differences...


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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 employability

Many jobs expect DBA to know multiple RDBMSWhy not learn one that is widely used?

And it's free you can download and install right now!


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Oracle DBA Perspective

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

Storage engines


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My Message

Compare MySQL to OracleNot to be critical of MySQLNot to praise Oracle

Make Oracle DBAs awareHow much we assume about RDBMSBecause Oracle does things a certain way

MySQL is very different

Assuming it is like Oracle can cause serious problemsDoes your business understand the differences?

The cost of being 'free'?


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MySQL Versions

MySQL EnterpriseHave to buy support

MySQL Community EditionThe 'free' version

MySQL Community Edition Preview Release Available for downloadReady for prime time?

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


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MySQL Versions


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MySQL Where Did It Come From?

Used to store web site logsTransactions

What's that?

If we lose some recordsSo what?

Supported by an individualDo your own thing

RecoveryNot to worry, plenty more web logs every day


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Some Differences MySQL/Oracle

OracleDatabaseSchema

a group of database objects

Database user Maps to a database schemaMySQL

Server

DatabasesGroup of database objectsUsers don't map to database


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Some Differences MySQL/Oracle

Storage enginesTransaction supportPerformance

Hot backupBinary logging and recoveryTable locking

CorruptionMisc.


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Storage Engines

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

MySQL storage engines

MyISAM (IBM, Indexed Sequential Access Method)Very fast read

InnoDBTransactional, like Oracle

Separate software, owned by OracleMany others

See next chart


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Storage Engines


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InnoDB Storage Engine

Imagine mixingMyISAM, InnoDB tables in a statementWhat does 'transactional' mean?

What does recovery mean?


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CSV Storage Engine

CSV storage engineStores data in text filesUsing comma-separated format


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Blackhole Storage Engine

My favorite

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


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Yeah, But...

No problemI'll just make all the tables InnoDB

Cool, but

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

Privileged usersNo one should do this, but...stuff happens

Create table syntaxSupports overriding default storage engine


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Transaction Support

MyISAMDefault table typeTable type of system databases

Does not support transactionsExample

Writing to MyISAM tables and server crashesWho know what was and wasn't written to tablesNo recovery


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Performance

Many large MySQL servers in usePerformance must be goodor good enough for 'free'

Optimizer Different storage enginesHow to optimize statement that has

MyISAM tablesInnoDB tables

Does it support all storage engines you are using?


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Hot BackupMySQL does not have this

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

Backup option #2

Lock all tablesDump all data to a dump file

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

Backup option #3Buy hot backup software product

Not free


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Binary Logging and Recovery

MySQLDefault, no loggingYou can configure binary logging

Three formatsStatement-basedRow-basedMixed

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


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MySQL Binary Logs

MySQL does not have any way of knowingwhen replaying the binary logs whichstatements need to be executed and which arealready committed.

Oracle DBA doesn't worry about thisOracle checks and tells you which archived redo logis needed nextOracle won't allow archived redo logs to be appliedout of order


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Binary Logging Formats


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Binary Log Issues


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Table Locking

MyISAM storage engineDoes not support row level locking

Table locks

Performance?InnoDB storage engine

Supports row level locking


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Corruption

OracleI have rarely seen any casesBut all tables support transactions

MySQLWhat does it mean to rollback

When different storage engines involvedSome support transactions, some don'tSome tables will be rolled back

Others won't

Is this corruption?


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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/


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MySQL Issues

MiscReferential Integrity

Some storage engines support

TriggersRow-level, not statement-level

DirectloadNot supported

Parallel QueryNot supported


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MySQL Issues

White Paper Compares MySQL to PostgreSQL

PostgreSQL, another open source RDBMS

More like Oracle than MySQLDiscusses issues with MySQL

I'm not endorsing PostgreSQLBut the whitepaper is very good

GooglePostgreSQL vs. MySQL A Comparison of EnterpriseSuitability


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MySQL Table Storage

MyISAMEach table has three files

.frm Data dictonary information

.MYD table data.MYI table indexes

InnoDBData and indexes in a tablespaces

Made up of one or more datafilesSound familiar?


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Documentation Online


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Talk Is Cheap

A little less conversation A little more action

Download and install MySQL to your laptop now

Slides show the stepsWindows

You will have a fully functional MySQL server

Start learning right now


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Install MySQL Windows

Windows Vista6.0 Service Pack 1Screenshots shown

Windows XPProfessional Version 5.1Same steps

Very minor differences in what you see


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Downloads?


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Downloads?


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Enterprise Version


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Community Version


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Windows Downloads


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Windows Installation


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d ll


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i d ll i


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Wi d I ll i


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Wi d I ll i


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Wi d I t ll ti


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Wi d I t ll ti


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Wi d I t ll ti


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Uncheck



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Check



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mysql



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Accessing MySQL Windows


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Click StartProgramsMySQLMySQL Server 5.1MySQL Command Line Client

Right-clickSend to

Desktop (Create Shortcut)

Double-click desktop iconMySQL Command Line Client



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mysql

Shortcut created at installation

mysql client utility


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mysql client utility

Similar to SQL*Plus

Now What?


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Now What?Stop, start MySQL server

What databases are availableshow databases;

Set default databaseuse

What tables are in the databaseshow tables;

Windows Vista


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Windows Vista

Stop/StartServices

StartSettingsControl PanelSystem and Maintenance

Administrative ToolsServices

Scroll down to MySQL, highlightUpper left, options for Stop, Pause, RestartIf MySQL is down, option to Start

Windows XP


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Windows XPStop/Start

Command linenet stop mysql, net start mysql

ServicesStartControl Panel

Administrative ToolsServices

Services window

Scroll down to MySQL, highlightUpper left, options for Stop, Pause, RestartIf MySQL is down, option to Start


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System Databases


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y

INFORMATION_SCHEMACatalog database

MYSQL database

User and privilege informationTEST

For you to play in...

These databases are created at installation

MySQL Server Configuration


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y Q gControlled by 'option' file(s)

Similar to Oracle pfile or spfileSHOW VARIABLES

See current values

Standard location(s)Search order

One of the most common problemsPersons don't know where these files areMake changes that don't take affectCan't find the file or files

Option File(s)


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p ( )MySQL searches multiple locations

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

mysql help

Note: dash dash help

Option File


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p

Option File


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p

Option File


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Option File


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Option File


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MySQL Filesystem Layout


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From option file (my.ini)basedir

Where software is stored

datadir Where table data is stored

MySQL basedir


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MySQL basedir/bin


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MySQL datadir


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MySQL Log Files


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General Query Log All client requests

Binary Log

Statements that modify dataSlow Query Log

Statements that take longer than 10 seconds

Error LogServer messages

MySQL Log Files


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Find log file locations

Summary


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

Hot backup for example

MySQL is widely used

MySQL is very different from OracleDBA tasks and issues will be different

MySQL is not better or worse than OracleJust very different

The End?


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You now have a MySQL server installedNo excuses

Learn it, live it, love it

Update your resumeNext?

Multiple MySQL servers on same machine

Replicationetc.

Documents

MySQL Would You Like Transactions