2013_scaladays

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Slick vs ORMJan Christopher Vogt, EPFL

Stefan Zeiger, Typesafe

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Object-Orientation + Relational

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Functional + Relational

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Slick is a Functional-Relational Mapper

embraces relational (not hidden)

natural fit (no impedance mismatch) stateless (not stateful)

Slick is to ORM what Scala is to Java

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8 Reasons for using Slick

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Sample App Data Model

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1Scala collection-like

API

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Scala collection-like API

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2

Minimal configuration

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Configuration

Do mappings in Scala

No XML, no "magic" behind the scenes

Connect to a JDBC URL or DataSource

Use an external connection pool

Wrap raw JDBC connections for use with DI

containers that handle the transactionmanagement

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Connect

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3Loosely-coupled, flexible

mapping

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Keep Your Data Model Clean

caseclassDevice(id: Long,

price: Double,

acquisition: Date)

classDevices extendsTable[Device](DEVICE ) {

defid = column[Long](ID , O.PrimaryKey)

defprice = column[String](PRICE )

defacquisition = column[Date](ACQUISITION )

def* = id ~ price ~ acquisition

(Device.apply _, Device.unapply _)

}

valDevices = newDevices

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classDevices extendsTable[(Long, String, Date)](DEVICE ) {





}


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caseclassDevice(id: Long,

price: Double,

acquisition: Date)

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Custom Column Types

caseclassDevice(id: DeviceId, )

classDeviceId(valid: Long) extendsAnyVal

implicitvaldeviceIdType= MappedTypeMapper.base

[DeviceId, Long](_.id, newDeviceId(_))


defid = column[DeviceId](ID , O.PrimaryKey)

}

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Custom Functions

defdayOfWeek(c: Column[Date]) =

SimpleFunction[Int]("DAY_OF_WEEK").apply(Seq(c))

valdows= Query(Devices).map { d =>

(d.id, dayOfWeek(d.acquisition)) }.run

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(Device.apply _, Device.unapply _)

}


Work With Any DB Schema

You define the schema:

3, 1': ?.'+4&'

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4Explicit control over

execution and transfer

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Execution is always explicit

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Example Data Model

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Transferred data

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()*.,

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5Predictable SQL

structure

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Predictable SQL structure

>;*#7%)*+,-*.6

1!,8

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6

Plain SQL support

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Plain SQL support

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7

Type Safety

o

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Enforce schema consistency

Generate DDL from table objects

Slick 2.0: Generate table objects and mapped

classes from database

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Compile-Time Safety

Spelling mistake in column name?

Wrong column type?

Mapped to the wrong class?

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Error messages can destroy the illusion

Compile-Time Safety

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(before we get to #8)

Relationship Queries

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Relationships

ORM

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Joins

()*.,

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Auto joins (1-n)

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Join types

.,

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Example Data Model

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) *

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Auto joins (n-n)

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Complex Auto Joins (n-n, etc.)

!"#*!+!& /.,9;

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Modifying relationships

query for what you want to modify

insert / update that query

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()*.,

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What about Inheritance?

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Example Data Model

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Inheritance

Relational does not support inheritance

Use relationships instead, you wont loose

(think has role instead of is a)

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Example Data Model

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Example Data Model

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Joining all sub-classes

a re-usable querythat joinsSites with ResearchSites and ProductionSites

.,

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You can do inheritance

+*)33 P,

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8composable /

re-usable queries

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Mental paradigm shi!

The ORM Way: Executor APIs (DAOs)

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Write query libraries

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Row functions

+*)33P,

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Row functions

traitHasName{

this:Table[_] =>

defname = column( ... )

...

defnameLike( pattern:Column[String] ) : Column[Boolean]

= this.name.toLowerCase like pattern.toLowerCase

}

classSites extendsTable[Site] withHasName

classComputers extendsTable[Computer] withHasName

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Query functions

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Refinements

method extensions (implicit conversions)

Option support using Slicks OptionMapper

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Suggestedslick app architecture

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Suggested Slick app architecture

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Outlook

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Slick 2.0

Coming Q3 / 2013

Query scheduling

Improved driver architecture

BasicProfile >: RelationalProfile >: SqlProfile >:JdbcProfile

Generate Slick code from database schemas

Proper "type providers" need new Scala More to come

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Extra slides

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Join via foreign key

2013_scaladays

Documents

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