orm dont kill your db, developers do

http://www.flickr.com/photos/hoyvinmayvin/5103806609/

Database

Developers

Guilherme BlancoThursday, March 1, 2012

ORMs donʼt kill your DB, developers do!

@guilhermeblanco

http://github.com/guilhermeblanco

Learning about good ORM practices on @guilhermeblanco

talk at @confooca!

InstaClick Inc.

Thursday, March 1, 2012

Agenda

http://www.flickr.com/photos/emerzh/3072428824/Thursday, March 1, 2012

General Rule

RTFMThursday, March 1, 2012

Dependency management

http://www.flickr.com/photos/ollesvensson/3694625903/Thursday, March 1, 2012

Dependency Management

Dependency Managementnamespace App\Bundle\BlogBundle\Entity;

/** * @ORM\Entity */class Post{ /** * @ORM\OneToMany( * targetEntity="AppComment:Comment", * mappedBy="post" * ) */ protected $comments;}

namespace App\Bundle\CommentBundle\Entity;

/** * @ORM\Entity */class Comment{ /** * @ORM\ManyToOne( * targetEntity="AppBlog:Post", * inversedBy="comments" * ) */ protected $post;}

namespace App\Bundle\BlogBundle\Entity;

/** * @ORM\Entity */class Post{ // ...}

namespace App\Bundle\CommentBundle\Entity;

/** * @ORM\Entity */class Comment{ /** * @ORM\ManyToOne(targetEntity="AppBlog:Post") */ protected $post;}

Fetch Mode

http://www.flickr.com/photos/comedynose/5318259802/Thursday, March 1, 2012

Fetch Mode

A fetching strategy is what ORM will use to retrieve associated objects if the application needs to navigate

through them

Fetch Mode

Supported by all association types...

Fetch Mode

• OneToOne

• OneToMany

• ManyToOne

• ManyToMany

Fetch Mode

Available fetch modes...

Fetch Mode

• EAGER

• LAZY (default)

• EXTRA_LAZY

Fetch Mode

• EAGER

• LAZY (default)

• EXTRA_LAZY

An association (collection or attribute), is fetched immediately when owner is loaded

Fetch Mode

• EAGER

• LAZY (default)

• EXTRA_LAZY

An association (collection or attribute), is fetched when the application invokes

an operation over it

Fetch Mode

• EAGER

• LAZY (default)

• EXTRA_LAZY

An association (collection or attribute), is fetched when the application invokes

an operation over it

Individual elements from association are accessed from Database as needed. ORM

does not fetch the whole association unless it is absolutely necessary

Fetch Mode/** * @ORM\Entity */class Post { /** * @ORM\ManyToOne(targetEntity="User", fetchMode="EAGER") */ protected $author;

/** * @ORM\ManyToMany(targetEntity="Tags", fetchMode="EXTRA_LAZY") * @ORM\JoinTable(name="posts_tags") */ protected $tagList;}

/** * @ORM\Entity */class Comment { /** * @ORM\OneToMany(targetEntity="Post", fetchMode="LAZY") * @JoinColumn(name="post_id", referencedColumnName="id") */ protected $post;}

Fetch Mode/** * @ORM\Entity */class Post { /** * @ORM\ManyToOne(targetEntity="User", fetchMode="EAGER") */ protected $author;

/** * @ORM\ManyToMany(targetEntity="Tags", fetchMode="EXTRA_LAZY") * @ORM\JoinTable(name="posts_tags") */ protected $tagList;}

/** * @ORM\Entity */class Comment { /** * @ORM\OneToMany(targetEntity="Post", fetchMode="LAZY") * @JoinColumn(name="post_id", referencedColumnName="id") */ protected $post;}

Deadly sin

Querying

http://www.flickr.com/photos/pschadler/4932737690/Thursday, March 1, 2012

Querying

$query = $entityManager->createQuery(' SELECT p FROM Post p');$postList = $query->getResult();

foreach ($postList as $post) { $tagList = $post->getTagList();

foreach ($tagList as $tag) { echo $tag->getName(); }}

Querying

$query = $entityManager->createQuery(' SELECT p FROM Post p');$postList = $query->getResult();

N + 1 trolls?

Querying

$query = $entityManager->createQuery(' SELECT p, t FROM Post p LEFT JOIN p.tagList t');$postList = $query->getResult();

Querying

$query = $entityManager->createQuery(' SELECT p, t FROM Post p LEFT JOIN p.tagList t');$postList = $query->getResult();

Pardon? DQL is powerful! RTFM

Querying

I know you all don’t trust me...

Querying

...but take a look at its EBNF grammar...

QueryLanguage ::= SelectStatement | UpdateStatement | DeleteStatementSelectStatement ::= SelectClause FromClause [WhereClause] [GroupByClause] [HavingClause] [OrderByClause]UpdateStatement ::= UpdateClause [WhereClause]DeleteStatement ::= DeleteClause [WhereClause]JoinAssociationPathExpression ::= IdentificationVariable "." (CollectionValuedAssociationField | SingleValuedAssociationField)AssociationPathExpression ::= CollectionValuedPathExpression | SingleValuedAssociationPathExpressionSingleValuedPathExpression ::= StateFieldPathExpression | SingleValuedAssociationPathExpressionStateFieldPathExpression ::= IdentificationVariable "." StateField | SingleValuedAssociationPathExpression "." StateFieldSingleValuedAssociationPathExpression ::= IdentificationVariable "." SingleValuedAssociationFieldCollectionValuedPathExpression ::= IdentificationVariable "." {SingleValuedAssociationField "."}* CollectionValuedAssociationFieldStateField ::= {EmbeddedClassStateField "."}* SimpleStateFieldSimpleStateFieldPathExpression ::= IdentificationVariable "." StateFieldSelectClause ::= "SELECT" ["DISTINCT"] SelectExpression {"," SelectExpression}*SimpleSelectClause ::= "SELECT" ["DISTINCT"] SimpleSelectExpressionUpdateClause ::= "UPDATE" AbstractSchemaName ["AS"] AliasIdentificationVariable "SET" UpdateItem {"," UpdateItem}*DeleteClause ::= "DELETE" ["FROM"] AbstractSchemaName ["AS"] AliasIdentificationVariableFromClause ::= "FROM" IdentificationVariableDeclaration {"," IdentificationVariableDeclaration}*SubselectFromClause ::= "FROM" SubselectIdentificationVariableDeclaration {"," SubselectIdentificationVariableDeclaration}*WhereClause ::= "WHERE" ConditionalExpressionHavingClause ::= "HAVING" ConditionalExpressionGroupByClause ::= "GROUP" "BY" GroupByItem {"," GroupByItem}*OrderByClause ::= "ORDER" "BY" OrderByItem {"," OrderByItem}*Subselect ::= SimpleSelectClause SubselectFromClause [WhereClause] [GroupByClause] [HavingClause] [OrderByClause]UpdateItem ::= IdentificationVariable "." (StateField | SingleValuedAssociationField) "=" NewValueOrderByItem ::= (ResultVariable | SingleValuedPathExpression) ["ASC" | "DESC"]GroupByItem ::= IdentificationVariable | SingleValuedPathExpressionNewValue ::= ScalarExpression | SimpleEntityExpression | "NULL"IdentificationVariableDeclaration ::= RangeVariableDeclaration [IndexBy] {JoinVariableDeclaration}*SubselectIdentificationVariableDeclaration ::= IdentificationVariableDeclaration | (AssociationPathExpression ["AS"] AliasIdentificationVariable)JoinVariableDeclaration ::= Join [IndexBy]RangeVariableDeclaration ::= AbstractSchemaName ["AS"] AliasIdentificationVariableJoin ::= ["LEFT" ["OUTER"] | "INNER"] "JOIN" JoinAssociationPathExpression ["AS"] AliasIdentificationVariable ["WITH" ConditionalExpression]IndexBy ::= "INDEX" "BY" SimpleStateFieldPathExpressionSelectExpression ::= IdentificationVariable | PartialObjectExpression | (AggregateExpression | "(" Subselect ")" | FunctionDeclaration | ScalarExpression) [["AS"] AliasResultVariable]SimpleSelectExpression ::= ScalarExpression | IdentificationVariable | (AggregateExpression [["AS"] AliasResultVariable])PartialObjectExpression ::= "PARTIAL" IdentificationVariable "." PartialFieldSetPartialFieldSet ::= "{" SimpleStateField {"," SimpleStateField}* "}"ConditionalExpression ::= ConditionalTerm {"OR" ConditionalTerm}*ConditionalTerm ::= ConditionalFactor {"AND" ConditionalFactor}*ConditionalFactor ::= ["NOT"] ConditionalPrimaryConditionalPrimary ::= SimpleConditionalExpression | "(" ConditionalExpression ")"SimpleConditionalExpression ::= ComparisonExpression | BetweenExpression | LikeExpression | InExpression | NullComparisonExpression | ExistsExpression | EmptyCollectionComparisonExpression | CollectionMemberExpression | InstanceOfExpressionEmptyCollectionComparisonExpression ::= CollectionValuedPathExpression "IS" ["NOT"] "EMPTY"CollectionMemberExpression ::= EntityExpression ["NOT"] "MEMBER" ["OF"] CollectionValuedPathExpressionLiteral ::= string | char | integer | float | booleanInParameter ::= Literal | InputParameterInputParameter ::= PositionalParameter | NamedParameterPositionalParameter ::= "?" integerNamedParameter ::= ":" stringArithmeticExpression ::= SimpleArithmeticExpression | "(" Subselect ")"SimpleArithmeticExpression ::= ArithmeticTerm {("+" | "-") ArithmeticTerm}*ArithmeticTerm ::= ArithmeticFactor {("*" | "/") ArithmeticFactor}*ArithmeticFactor ::= [("+" | "-")] ArithmeticPrimaryArithmeticPrimary ::= SingleValuedPathExpression | Literal | "(" SimpleArithmeticExpression ")" | FunctionsReturningNumerics | AggregateExpression | FunctionsReturningStrings | FunctionsReturningDatetime | IdentificationVariable | InputParameter | CaseExpressionScalarExpression ::= SimpleArithmeticExpression | StringPrimary | DateTimePrimary | StateFieldPathExpression | BooleanPrimary | EntityTypeExpression | CaseExpressionStringExpression ::= StringPrimary | "(" Subselect ")"StringPrimary ::= StateFieldPathExpression | string | InputParameter | FunctionsReturningStrings | AggregateExpression | CaseExpressionBooleanExpression ::= BooleanPrimary | "(" Subselect ")"BooleanPrimary ::= StateFieldPathExpression | boolean | InputParameterEntityExpression ::= SingleValuedAssociationPathExpression | SimpleEntityExpressionSimpleEntityExpression ::= IdentificationVariable | InputParameterDatetimeExpression ::= DatetimePrimary | "(" Subselect ")"DatetimePrimary ::= StateFieldPathExpression | InputParameter | FunctionsReturningDatetime | AggregateExpressionAggregateExpression ::= ("AVG" | "MAX" | "MIN" | "SUM") "(" ["DISTINCT"] StateFieldPathExpression ")" | "COUNT" "(" ["DISTINCT"] (IdentificationVariable | SingleValuedPathExpression) ")"CaseExpression ::= GeneralCaseExpression | SimpleCaseExpression | CoalesceExpression | NullifExpressionGeneralCaseExpression ::= "CASE" WhenClause {WhenClause}* "ELSE" ScalarExpression "END"WhenClause ::= "WHEN" ConditionalExpression "THEN" ScalarExpressionSimpleCaseExpression ::= "CASE" CaseOperand SimpleWhenClause {SimpleWhenClause}* "ELSE" ScalarExpression "END"CaseOperand ::= StateFieldPathExpression | TypeDiscriminatorSimpleWhenClause ::= "WHEN" ScalarExpression "THEN" ScalarExpressionCoalesceExpression ::= "COALESCE" "(" ScalarExpression {"," ScalarExpression}* ")"NullifExpression ::= "NULLIF" "(" ScalarExpression "," ScalarExpression ")"QuantifiedExpression ::= ("ALL" | "ANY" | "SOME") "(" Subselect ")"BetweenExpression ::= ArithmeticExpression ["NOT"] "BETWEEN" ArithmeticExpression "AND" ArithmeticExpressionComparisonExpression ::= ArithmeticExpression ComparisonOperator ( QuantifiedExpression | ArithmeticExpression )InExpression ::= StateFieldPathExpression ["NOT"] "IN" "(" (InParameter {"," InParameter}* | Subselect) ")"InstanceOfExpression ::= IdentificationVariable ["NOT"] "INSTANCE" ["OF"] (InstanceOfParameter | "(" InstanceOfParameter {"," InstanceOfParameter}* ")")InstanceOfParameter ::= AbstractSchemaName | InputParameterLikeExpression ::= StringExpression ["NOT"] "LIKE" string ["ESCAPE" char]NullComparisonExpression ::= (SingleValuedPathExpression | InputParameter) "IS" ["NOT"] "NULL"ExistsExpression ::= ["NOT"] "EXISTS" "(" Subselect ")"ComparisonOperator ::= "=" | "<" | "<=" | "<>" | ">" | ">=" | "!="FunctionDeclaration ::= FunctionsReturningStrings | FunctionsReturningNumerics | FunctionsReturningDateTimeFunctionsReturningNumerics ::= "LENGTH" "(" StringPrimary ")" | "LOCATE" "(" StringPrimary "," StringPrimary ["," SimpleArithmeticExpression]")" | "ABS" "(" SimpleArithmeticExpression ")" | "SQRT" "(" SimpleArithmeticExpression ")" | "MOD" "(" SimpleArithmeticExpression "," SimpleArithmeticExpression ")" | "SIZE" "(" CollectionValuedPathExpression ")"FunctionsReturningDateTime ::= "CURRENT_DATE" | "CURRENT_TIME" | "CURRENT_TIMESTAMP"FunctionsReturningStrings ::= "CONCAT" "(" StringPrimary "," StringPrimary ")" | "SUBSTRING" "(" StringPrimary "," SimpleArithmeticExpression "," SimpleArithmeticExpression ")" | "TRIM" "(" [["LEADING" | "TRAILING" | "BOTH"] [char] "FROM"] StringPrimary ")" | "LOWER" "(" StringPrimary ")" | "UPPER" "(" StringPrimary ")"

Querying

Since the letter size is 6, you may still not believe me

Querying

let’s try a real world example!

Querying

Do you know Facebook activity wall?

Querying

Do you know Facebook activity wall?Let’s show it!

SELECT e, a FROM Entry e JOIN e.wall w JOIN e.user u LEFT JOIN u.avatar av WHERE u = :user OR w IN ( SELECT uw FROM UserWall uw WHERE uw.user = :user OR uw.user IN ( SELECT CASE WHEN ua = us.subscriber THEN ub.id ELSE ua.id END FROM UserSubscription us JOIN us.friendship f JOIN f.userA ua JOIN f.userB ub WHERE us.muted = FALSE AND us.subscriber = :user AND f.status = 'Approved' ) ) OR w IN ( SELECT gw FROM GroupWall gw WHERE gw.group IN ( SELECT DISTINCT g.id FROM GroupSubscription gs JOIN gs.group g WHERE gs.subscriber = :user AND gs.muted = FALSE AND gs.status = 'Approved' ) ) ORDER BY e.created DESC

Entry you wrote

Entry was in your Wall

Entry you wrote

User is your friend, the friendship is approved and subscription is not muted

Entry you wrote

User is your friend, the friendship is approved and subscription is not muted

Group that you participate, is not muted and have an approved status

Caching

http://www.flickr.com/photos/eszter/3851576235/Thursday, March 1, 2012

Caching

Doctrine supports 3 levels of caching...

Caching

• Metadata cache

• Query cache

• Result cache

Caching

• Metadata cache

• Query cache

• Result cache

Cache mapping of entities

Caching

• Metadata cache

• Query cache

• Result cache

Cache DQL to SQL conversion

Caching

• Metadata cache

• Query cache

• Result cache

Cache PDO result set

Cache DQL to SQL conversion

Caching

$query = $entityManager->createQuery(' SELECT p FROM Post p');

$query->useResultCache(true, 600, 'find-all-posts');

$postList = $query->getResult();

Indexing

http://www.flickr.com/photos/osuarchives/2659419894/Thursday, March 1, 2012

Indexing

Doctrine is able to hint the Schema Tool to generate database indexes on specified table columns

Indexing/** * @ORM\Entity * @ORM\Table( * name = "users", * uniqueConstraints = { * @ORM\UniqueConstraint( * name = "user_unique", * columns = { "name" } * ) * }, * indexes = { * @ORM\Index( * name = "login_idx", * columns = { "name", "password" } * ) * } * ) */class User{ // ...}

Indexing

@ORM\UniqueConstraint( name = "user_unique", columns = { "name" })

CREATE UNIQUE INDEX user_unique ON TABLE users (name);

Indexing

@ORM\Index( name = "login_idx", columns = { "name", "password" })

CREATE INDEX login_idx ON TABLE users (name, password);

Indexing

@ORM\Index( name = "login_idx", columns = { "name", "password" })

CREATE INDEX login_idx ON TABLE users (name, password);

Some drivers restrict to 32 chars as index name

Inheritance

http://www.flickr.com/photos/duanekeys/307005468/Thursday, March 1, 2012

Inheritance

Inheritance is a very deep topic in ORMs

Inheritance

Each inheritance type has advantages and disadvantages

Inheritance

• Concrete Table Inheritance

• Single Table Inheritance

• Class Table Inheritance

Inheritance

One Class, one Table

Inheritance

Multiple Classes, one Table

Inheritance

Multiple Classes, one Table

Multiple Classes, multiple Tables

Inheritance

• Pros

Inheritance

• Pros• No locking problems

Inheritance

• No irrelevant columns

Inheritance

• Cons

Inheritance

• Cons• Difficult to deal with primary keys

Inheritance

• Search base class means search all tables

Inheritance

• Search base class means search all tables

• Update on columns means update on all hierarchy tables

Inheritance/** * @ORM\MappedSuperclass */class Person{ /** * @ORM\Column(type="string", length=50) */ protected $firstName;

/** * @ORM\Column(type="string", length=50) */ protected $lastName;}

/** * @ORM\Entity * @ORM\Table(name="users") */class User extends Person{ /** * @ORM\Id * @ORM\GeneratedValue * @ORM\Column(type="integer") */ protected $id;}

Inheritance

CREATE TABLE users ( id INTEGER AUTO_INCREMENT NOT NULL, firstName VARCHAR(50) NOT NULL, lastName VARCHAR(50) NOT NULL, PRIMARY KEY (id)) ENGINE=InnoDB;

Inheritance

• Pros

Inheritance

• Pros• Only one table for hierarchy

Inheritance

• No joins

Inheritance

• No joins

• Refactoring of fields means no change to database table

Inheritance

• No joins

• Cons

Inheritance

• No joins

• Cons• Waste of space in database

Inheritance

• No joins

• Too many locks due to many accesses

Inheritance

• No joins

• Too many locks due to many accesses

• No duplicated field names with different meanings

Inheritancenamespace MyApp\Entity;

/** * @ORM\Entity * @ORM\Table(name= "people") * @ORM\InheritanceType("SINGLE_TABLE") * @ORM\DiscriminatorColumn(name="discr", type="string") * @ORM\DiscriminatorMap({ * "user" = "MyApp\Entity\User", * "employee" = "MyApp\Entity\Employee" * }) */class User{ // ...}

/** * @ORM\Entity */class Employee extends User{ // ...}

Inheritance

CREATE TABLE people ( id INT AUTO_INCREMENT NOT NULL, firstName VARCHAR(50) NOT NULL, lastName VARCHAR(50) NOT NULL, discr VARCHAR(20) NOT NULL, role VARCHAR(100) DEFAULT NULL, PRIMARY KEY (id)) ENGINE=InnoDB;

Inheritance

• Pros

Inheritance

• Pros• Easy to understand

Inheritance

• Database space is optimized due to table normalization

Inheritance

• Direct relationship between Domain Model and Database

Inheritance

• Cons

Inheritance

• Cons• Too many joins

Inheritance

• Refactoring of fields needs a database schema update

Inheritance

• Refactoring of fields needs a database schema update

• Superclass table accessed a lot, it means it may enter in lock mode

Inheritancenamespace MyApp\Entity;

/** * @ORM\Entity * @ORM\Table(name="users") * @ORM\InheritanceType("JOINED") * @ORM\DiscriminatorColumn( * name = "discr", * type = "string", * length = 20 * ) * @ORM\DiscriminatorMap({ * "user" = "MyApp\Entity\User", * "employee" = "MyApp\Entity\Employee" * }) */class User{ // ...}

/** * @ORM\Entity * @ORM\Table(name= "employees") */class Employee extends User{ // ...}

Inheritance

CREATE TABLE users ( id INT AUTO_INCREMENT NOT NULL, firstName VARCHAR(50) NOT NULL, lastName VARCHAR(50) NOT NULL, discr VARCHAR(20) NOT NULL, PRIMARY KEY (id)) ENGINE = InnoDB;

CREATE TABLE employees ( id INT NOT NULL, role VARCHAR(100) NOT NULL, PRIMARY KEY (id)) ENGINE = InnoDB;

ALTER TABLE employees ADD CONSTRAINT FK_BA82C300BF396750 FOREIGN KEY (id) REFERENCES users (id) ON DELETE CASCADE;

Inheritance

What’s the problem with inheritance?

Inheritance

What’s the problem with inheritance?Hydration

Inheritance

• Inverse side *ToOne

Inheritance

• Owning side *ToOne with Inheritance

Inheritance

• Owning side *ToOne with Inheritance

• Disabled deferEagerLoad while Querying

Cascades

http://www.flickr.com/photos/over_kind_man/3158552109/Thursday, March 1, 2012

Cascades

Ability to tell Unit Of Work of Doctrine how it should act when inspecting an association for graph changes

Cascades

Use judiciously

Cascades

It can heavily increase the graph edges to be navigated once the Compute Changeset algorithm is ran

Cascades

This means more time to persist, delete, merge, detach, refresh...

Cascades

/** * @ORM\Entity */class User{ //...

/** * Bidirectional - One-To-Many (INVERSE SIDE) * * @ORM\OneToMany( * targetEntity = "Comment", * mappedBy = "author", * cascade = { "persist", "remove" } * ) */ protected $commentsAuthored;}

Hydrators

http://crimsonnightstock.deviantart.com/art/Yellow-Fire-Hydrant-Stock-100121929Thursday, March 1, 2012

Hydrators

Doctrine comes with some useful result hydrators

Hydrators

This means that not all times you need to retrieve objects

Hydrators

• Object

• Array

• Scalar

• Iterable

• Simple Object

• Single Scalar

Hydrators

• Object

• Array

• Scalar

• Iterable

• Simple Object

• Single Scalar

$resultList = $query->getResult();

Hydrators

• Object

• Array

• Scalar

• Iterable

• Simple Object

• Single Scalar

$resultArray = $query->getArrayResult();

Hydrators

• Object

• Array

• Scalar

• Iterable

• Simple Object

• Single Scalar

$result = $query->getScalarResult();

Hydrators

• Object

• Array

• Scalar

• Iterable

• Simple Object

• Single Scalar

$iterator = $query->iterate();

Hydrators

• Object

• Array

• Scalar

• Iterable

• Simple Object

• Single Scalar

$result = $query->getSingleResult();

Hydrators

• Object

• Array

• Scalar

• Iterable

• Simple Object

• Single Scalar

$result = $query->getSingleResult();

$result = $query->getSingleScalarResult();

http://joind.in/6053

Questions?

@guilhermeblanco

InstaClick Inc.

Questions?

@guilhermeblanco

InstaClick Inc. We are hiring! Talk to me privately if interested

Questions?Thank you!

@guilhermeblanco

InstaClick Inc. We are hiring! Talk to me privately if interested

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