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State-Based or Migrations-Based Database Development?

A Review of the Pros and Cons…Alex Yates

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DLM Consultant

workingwithdevs.com

alex.yates@dlmconsultants.com

Alex Yates

@_AlexYates_

@_AlexYates_

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AgileScrumLeanIterativeContinuous Delivery

Developers

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MonitoringDeployment

IntegrityPerformance

DBAs

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Woah! Deployment fail?

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#worksOnMyMachine

Woah! Deployment fail?

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A cursor?! You just CAN’T do that?!

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#worksOnMyMachine

A cursor?! You just CAN’T do that?!

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Hey, you just dropped my hot-fix!

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#worksOnMyMachine

Hey, you just dropped my hot-fix!

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Farm Credit Services of America (FCSA)

• 100 person IT team, 14 sub-teams• Database version control inconsistent

• Deployment process manual• Delivery was slow and

unreliable

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Farm Credit Services of America (FCSA)

• Deployments easier to review

• Delivery faster and more reliable

• Standardised source control and delivery process

• Automated manual deployment tasks

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The automated deployment pipeline

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Databases are hard

• Schema changes vs existing data• Reference data vs production data• Teamwork and testing• Database drift (change outside

process, e.g. production hot-fixes)

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There’s more than one way to skin a cat

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There’s more than one way to skin automatea cat

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V1 V2

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V1 V2

Migrations-based solutions

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V1 V2

State-based solutions

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“There's nothing more reliable than keeping track of exactly the scripts you intend to run, and running them, without trying to compare state and guess.”

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“There's nothing more reliable than keeping track of exactly the scripts you intend to run, and running them, without trying to compare state and guess.”

Paul Stovell, Octopus Deploy

http://docs.octopusdeploy.com/display/OD/SQL+Server+databases

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“As soon as you have multiple changes on a single aspect of an object, ordering and the ability to detect which change needs to be made gets very complicated.”

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“As soon as you have multiple changes on a single aspect of an object, ordering and the ability to detect which change needs to be made gets very complicated.”

Gert Drapers, built DataDude

https://blogs.msdn.microsoft.com/gertd/2009/06/05/declarative-database-development/

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Migrations vs state

http://workingwithdevs.com/delivering-databases-migrations-vs-state/

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Migrations vs state

http://workingwithdevs.com/delivering-databases-migrations-vs-state/

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Migrations vs state

http://workingwithdevs.com/delivering-databases-migrations-vs-state/

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Migrations vs state

http://workingwithdevs.com/delivering-databases-migrations-vs-state/

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Migrations vs state

http://workingwithdevs.com/delivering-databases-migrations-vs-state/

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Migrations vs state

http://workingwithdevs.com/delivering-databases-migrations-vs-state/

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Migrations vs state

http://workingwithdevs.com/delivering-databases-migrations-vs-state/

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11

2 Create view: kittenTrainersNrLdn

Selects only: kittenTrainers.FullName

Edit table: kittenTrainersAdd column: AcceptsTigerCubs BIT

Both work!Same changes, versioned and deployed two ways

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Demo

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11

2 Create view: kittenTrainersNrLdn

Selects only: kittenTrainers.FullName

Edit table: kittenTrainersAdd column: AcceptsTigerCubs BIT

Both work!Same changes, versioned and deployed two ways

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11Edit table: kittenTrainersSplit column trainerFullName

into trainerFirstName and trainerLastName

But both suck.A tale of two work items…

2

Edit view: kittenTrainersNrLdnAdd column: AcceptsTigerCubs

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0124_edit_view.sqlALTER VIEW kittenTrainersNrLdnAS SELECT fullName, acceptsTigerCubs FROM kittenTrainers

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0124_edit_view.sql 0125_edit_table.sqlALTER VIEW kittenTrainersNrLdnAS SELECT fullName, acceptsTigerCubs FROM kittenTrainers

ALTER TABLE kittenTrainers

*FUN WITH STRINGS* END

ALTER VIEW kittenTrainersNrLdnAS SELECT firstName, lastName FROM kittenTrainers

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ALTER TABLE kittenTrainers

*FUN WITH STRINGS* END

ALTER VIEW kittenTrainersNrLdnAS SELECT firstName, lastName FROM kittenTrainers

0124_edit_view.sql 0125_edit_table.sql

!

ALTER VIEW kittenTrainersNrLdnAS SELECT fullName, acceptsTigerCubs FROM kittenTrainers

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Conflicts easily missedChanges overwritten, hard to spot

Order mattersLast script wins

The “winding path” problem

How do you fix a bug that has been deployed to some environments but not others?

The problem with migrations

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V123kittenTrainersNrLdn.sqlCREATE VIEW kittenTrai…AS SELECT fullName FROM kittenTrainers

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V124kittenTrainersNrLdn.sqlCREATE VIEW kittenTrai…AS SELECT fullName, acceptsTigerCubs FROM kittenTrainers

V123kittenTrainersNrLdn.sqlCREATE VIEW kittenTrai…AS SELECT fullName FROM kittenTrainers

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V125kittenTrainersNrLdn.sqlCREATE VIEW kittenTrai…AS SELECT firstName, lastName FROM kittenTrainers

V124kittenTrainersNrLdn.sqlCREATE VIEW kittenTrai…AS SELECT fullName, acceptsTigerCubs FROM kittenTrainers

V123kittenTrainersNrLdn.sqlCREATE VIEW kittenTrai…AS SELECT fullName FROM kittenTrainers

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V125kittenTrainersNrLdn.sqlCREATE VIEW kittenTrai…AS SELECT firstName, lastName FROM kittenTrainers

V124kittenTrainersNrLdn.sqlCREATE VIEW kittenTrai…AS SELECT fullName, acceptsTigerCubs FROM kittenTrainers

V123kittenTrainersNrLdn.sqlCREATE VIEW kittenTrai…AS SELECT fullName FROM kittenTrainers

!

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REVISION 123 REVISION 124kittenTrainers.sqlCREATE TABLE kittenTrainers(fullName,

acceptsTigerCubs)kittenTrainersNrLdn.sqlCREATE VIEW kittenTrainersN…AS SELECT fullName

FROM kittenTrainers

kittenTrainers.sqlCREATE TABLE kittenTrainers(firstName, lastName, acceptsTigetCubs)

kittenTrainersNrLdn.sqlCREATE VIEW kittenTrainersN…AS SELECT firstName, lastName, acceptsTigerCubs FROM kittenTrainers

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Diff script:

DROP COLUMN fullName

ALTER TABLE kittenTrainers ADD FirstName NVARCHAR(50), LastName NVARCHAR(50)

ALTER VIEW kittenTrainersNrLdn AS  …

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Diff script:

DROP COLUMN fullName

ALTER TABLE kittenTrainers ADD FirstName NVARCHAR(50), LastName NVARCHAR(50)

ALTER VIEW kittenTrainersNrLdn AS  …

!

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Script:

DROP COLUMN fullName

ALTER TABLE kittenTrai… ADD FirstName, LastName

ALTER VIEW kittenTrain… AS  …

Need to understand your tool

It should be obvious to you that your tool won’t work

What is the Plan B / override?

Because one day you’ll need it

Test for data loss Automatically (naturally)

The problem with state

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So what is better?

State MigrationsVS

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State Easier (less control) Better for

sprocs/functions Better for

large/distributed teams Better for frequent

changes Better for dependency

nightmares Drift: rolled back

Migrations More control

(harder/needs discipline) Better for data

migrations Better for small teams Better for infrequent

changes Better for simple data

stores Drift: ignored

VS

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State Easier (less control) Better for

sprocs/functions Better for

large/distributed teams Better for frequent

changes Better for dependency

nightmares Drift: rolled back Better for development

Migrations More control

(harder/needs discipline) Better for data

migrations Better for small teams Better for infrequent

changes Better for simple data

stores Drift: ignored Better for automation

VS

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Pick appropriate tooling

State

DevArt SchemaCompare

DB Maestro

Migrations

DbUp

Flyway

Hybrid

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Let’s talk about:

https://msdn.microsoft.com/en-us/library/mt204009.aspx

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How does SSDT work?

Most scripts do not require manual scripting

Manual scripting causes problems

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How does SQL Source Control work?

Most scripts do not require manual scripting

Manual scripting causes problems

Perhaps just these ones?So only write these ones

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How does SSDT work?https://msdn.microsoft.com/en-US/library/hh272704(v=vs.103).aspx

https://msdn.microsoft.com/en-us/library/jj889461(v=vs.103).aspx

<< RefactorLog

Pre/Post-Deploy scripts >>

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Let’s talk about:

http://www.red-gate.com/sql-source-control/

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How does SQL Source Control work?

(This diagram again)We still only need a few upgrade scripts

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How does SQL Source Control work?

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How does SQL Source Control work?

https://documentation.red-gate.com/display/SOC5/How+migration+scripts+work c

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Let’s talk about:

http://www.red-gate.com/readyroll/

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State Easier (less control) Better for

sprocs/functions Better for

large/distributed teams Better for frequent

changes Better for dependency

nightmares Drift: rolled back

Migrations More control

(harder/needs discipline) Better for data

migrations Better for small teams Better for infrequent

changes Better for simple data

stores Drift: ignored

Better for sprocs/functions Better data migrations

How does ReadyRoll work?

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How does ReadyRoll work?Programmable objects

(Views, stored procedures etc)V125myproc.sqlEXEC sp_rename 'table_foo', 'table_bar‘

Migrations(Tables, reference data etc)

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How does ReadyRoll work?Programmable objects

(Views, stored procedures etc)V125myproc.sqlEXEC sp_rename 'table_foo', 'table_bar‘

Migrations(Tables, reference data etc)

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How does ReadyRoll work?Programmable objects

(Views, stored procedures etc)V125myproc.sqlEXEC sp_rename 'table_foo', 'table_bar‘

Migrations(Tables, reference data etc)

https://documentation.red-gate.com/display/RR1/Programmable+Objects

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But haven’t we been doing hybrid for years?

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ProdTestDev

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ProdTestDev

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ProdTestDev S0

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ProdTestDev S0

S0

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ProdTestDev S0

S0

State Migrations

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ProdTest

DevS0

“Late migrations”

S1

ProdTest

Dev S0

“Early migrations”

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Early vs Late

• Test deploy script early

• Easier to automate

• Developers own deployments (typically)

• Optimised deployment scripts (no winding path)

• Easier to intervene

• DBAs own deployments (typically)

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Drift

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“When making changes directly on production, you are making a decision that the delay due to poor cycle time is more expensive than the risk of making a mistake.”

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“When making changes directly on production, you are making a decision that the delay due to poor cycle time is more expensive than the risk of making a mistake.”

Alex Yates, Built this slide

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The bad stuff:

• Accidental roll-backs (state)

• Failed deployments (migrations)

• Environment inconsistency (migrations)

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DriftStrategies to help

Improve cycle time Strict security policies Monitor drift (play with DDL

triggers) Redgate DLM Dashboard

(free)https://www.simple-talk.com/sql/database-administration/database-deployment-the-bits-database-version-drift/

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DriftStrategies to help

Improve cycle time Strict security policies Monitor drift (play with DDL

triggers) Redgate DLM Dashboard

(free)http://www.red-gate.com/products/dlm/dlm-dashboard/

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Demo

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Farm Credit Services of America (FCSA)

• Standardised DLM processes• FCSA delivering much more efficiently

• The FCSA model being rolled out at FCMA (sister org)

• The team all have excellent CV’s

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Siloed sparrows suck at DLM

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Heated hippos are closed minded

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State Easier (less control) Better for

sprocs/functions Better for

large/distributed teams Better for frequent

changes Better for dependency

nightmares Drift: rolled back Better for development

Migrations More control

(harder/needs discipline) Better for data

migrations Better for small teams Better for infrequent

changes Better for simple data

stores Drift: ignored Better for automation

VS

Clever people consider options

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State

DevArt SchemaCompare

DB Maestro

Migrations

DbUp

Flyway

Hybrid

Hybrid tools are awesomeTools are pretty good

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ProdTest

DevS0

“Late migrations”

S1

ProdTest

Dev S0

“Early migrations”

It’s a balance, not a choice

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Hunt his smug face - make pain on it

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This stuff makes a big difference

http://www.codeaperture.io/2016/09/13/how-redgate-helped-define-our-process/

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Questions?

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DLM Consultant

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alex.yates@dlmconsultants.com

Alex Yates

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Image sourcesAuthor Source Information

Chiltepinster Wikimedia Commons Mocking Bird Argument.jpg – Wikimedia Commons. This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. Source on Wikimedia Commons: “Own work”

Bit Boy Flickr The elephant in the room – Flickr. This file is licensed under the Creative Commons Attribution 2.0 Generic license.

Nils Rinaldi Flickr Hippo fight 2/3 – Flickr. This file is licensed under the Creative Commons Attribution 2.0 Generic license.

My own collection Taken by/property of Alex Yates Kitten, “There’s more than one way to skin a cat!”

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