SlideShare a Scribd company logo
Database Programming
with Perl and
DBIx::Class
Dave Cross
dave@perlschool.co.uk
9th
February 2013
Perl School
 Low cost Perl training
 Training at all levels
 Trying to build a buzz about Perl
 Perl is not dead
 Perl is Modern
9th
February 2013
Xkcd Says
9th
February 2013
Your Help Please
 Trying to build a buzz about Perl
 You can help
 Please tell your friends
 Blog
 Twitter
 Facebook
 http://perlschool.co.uk
9th
February 2013
Upcoming Courses
 Perl School 5: Object Oriented Programming
with Perl and Moose
− 6th
April 2013
 Perl School 6: Database Programming with
Perl and DBIx::Class
− 8th
June 2013
 http://perlschool.co.uk/upcoming/
9th
February 2013
Admin Stuff
 Tickets
 Facilities
 Lunch
 Slides
 Feedback
9th
February 2013
Timings
 10:00 Session 1
 11:15 Break
 11:30 Session 2
 13:00 Lunch
 14:00 Session 3
 15:30 Break
 15:45 Session 4
 17:00 End
9th
February 2013
8
What We Will Cover
 Introduction to relational databases
 Introduction to databases and Perl
− DBI
− ORM
 Schema Classes
 Basic DB operations
− CRUD
9th
February 2013
9
What We Will Cover
 Advanced queries
− Ordering, joining, grouping
 Extending DBIC
 Deploying and updating schemas
 DBIC and Moose
 Further information
Relational Databases
9th
February 2013
11
Relational Databases
 A Relational Model of Data for Large
Shared Data Banks
− Ted Codd (1970)
 Applying relational calculus to databases
 See also Chris Date
− Database in Depth (2005)
− SQL and Relational Theory (2011)
− Database Design and Relational Theory (2012)
9th
February 2013
12
Relational Concepts
 Relation
− Table
− (Hence “relational”)
 Tuple
− Row
 Attribute
− Column
9th
February 2013
13
Some More Concepts
 Primary key
− Unique identifier for a row within a table
 Foreign key
− Primary key of a table that appears in another
table
− Used to define relationships between tables
− e.g artist_id in a table containing CDs
9th
February 2013
14
Referential Integrity
 Check that database is in a meaningful state
− No CDs without artist ID
− No artist IDs that don't exist in the artist table
 Constraints that ensure you can't break
referential integrity
− Don't delete artists that have associated CDs
− Don't insert a CD with a non-existent artist ID
9th
February 2013
15
SQL
 Structured Query Language
 Standard language for talking to databases
 Invented by IBM early 1970s
− SEQUEL
 ISO/ANSI standard
 Many vendor extensions
9th
February 2013
16
DDL & DML
 Two sides of SQL
 Data Definition Language
− Defines tables, etc
− CREATE, DROP, etc
 Data Manipulation Language
− Create, Read, Update, Delete data
− CRUD
− INSERT, SELECT, UPDATE, DELETE
Databases and Perl
9th
February 2013
18
Talking to Databases
 Database vendors supply an API
 Usually a C library
 Defines functions that run SQL against a DB
 All vendors' APIs do the same thing
 All vendors' APIs are completely different
9th
February 2013
19
Ancient History
 Perl 4 had ways to link to external libraries
− Like database APIs
 Static linking only
 Build a separate Perl binary for every
database
− oraperl, sybperl, etc
 Call API functions from Perl code
9th
February 2013
20
The Middle Ages
 Perl 5 introduced dynamic linking
 Load libraries at compile time
 Oraperl, Sybperl etc became CPAN modules
 use Oraperl;
 Still writing DB-specific code
9th
February 2013
21
Early Modern Era
 DBI.pm
 Standard database interface
 Database driver converts to API functions
− DBD::Oracle, DBD::Sybase, etc
 Code becomes more portable
 (Except for vendor extensions)
9th
February 2013
22
DBI Architecture
9th
February 2013
23
DBI Architecture
 Programmer writes code to DBI spec
 DBD converts code to database API
 DBD converts Perl data structures as
appropriate
 DBD converts returns data into Perl data
structures
9th
February 2013
24
Loading DBI
 use DBI;
 No need to load specific DBD library
− Sometimes DBD exports constants that you will
need
9th
February 2013
25
Connecting to DB
 Communicate with database through a
“database handle”
 my $dbh = DBI->connect(
'dbi:mysql:host=foo.com:database=foo',
$username, $password, %options
);
 Different DBDs have different options
 'mysql' defines the DBD to load
− DBD::mysql in this case
9th
February 2013
26
Selecting Data
 Select data using a prepare/execute/fetch
cycle
 my $sql = 'select col1, col2 from some_tab';
my $sth = $dbh->prepare($sql);
$sth->execute;
while (my $row = $sth->fetch) {
say join ' : ', @$row;
}
9th
February 2013
27
Inserting Data
 Insert data using a similar approach
 my $sql = 'insert into some_table (id, col1)
values (1, “Foo”)';
my $sth = $dbh->prepare($sql);
$sth->execute; # No fetch required
 Or using do(...) shortcut
 $dbh->do($sql);
9th
February 2013
28
Updating and Deleting
 Update or delete data in exactly the same
way
 my $sql = 'update some_table set col1 = “Bar”
where id = 1';
my $sth = $dbh->prepare($sql);
$sth->execute;
 Or
 $dbh->do('delete from some_table
where id = 1');
9th
February 2013
29
DBI Advantages
 Standard API for interacting with databases
 Programmer no longer needs to understand
vendor APIs
− Except the DBD author
 Increased programmer productivity
 Increased programmer flexibility
9th
February 2013
30
DBI Disadvantages
 Programmers still writing raw SQL
− Which is boring
− And error-prone
 DBI returns “dumb” data structures
− Arrays or hashes
− Often need to be converted into objects
9th
February 2013
31
DB Frameworks
 10 years ago people started writing SQL
generators
 Store a DB row in a hash
− DBI has a fetchrow_hashref() method
 Generate SQL for simple CRUD operations
9th
February 2013
32
Next Steps
 Turn those hashes into objects
 Class knows table name
 Class knows column names
 Class knows primary key
 SQL generation moved into superclass
 All DB tables have an associated class
Object Relational
Mapping
9th
February 2013
34
Relational Database
 Consider database storage structures
 A table defines a type of data that can be
stored
 A row is a single instance of that type of
data
 A column is an attribute of that instance
9th
February 2013
35
Object Oriented
 Consider OO storage structures
 A class defines a type of data that can be
stored
 An object is a single instance of that type of
data
 An attribute is an attribute of that instance
9th
February 2013
36
ORM
 Database concepts and OO concepts map
well onto each other
 A database table is a lot like an OO class
 A database row is a lot like an OO object
 A database column is a lot like an OO
attribute
 We can use this to make our lives easier
9th
February 2013
37
ORM Principles
 A Object Relational Mapper converts
between database data and objects
 In both directions
 Select data from the database and get an
object back
 Change that object and update the database
automatically
9th
February 2013
38
Replacing SQL
 Instead of
 SELECT *
FROM my_table
WHERE my_id = 10
 and then dealing with the
prepare/execute/fetch code
9th
February 2013
39
Replacing SQL
 We can write
 use My::Object;
# warning! not a real orm
my $obj = My::Object->retrieve(10)
 Or something similar
9th
February 2013
40
Perl ORM Options
 Plenty of choices on CPAN
 Fey::ORM
 Rose::DB
 Class::DBI
 DBIx::Class
− The current favourite
DBIx::Class
9th
February 2013
42
DBIx::Class
 Standing on the shoulders of giants
 Learning from problems in Class::DBI
 More flexible
 More powerful
9th
February 2013
43
DBIx::Class Example
 Modeling a CD collection
 Three tables
 artist (id, name)
 cd (id, artist_id, title, year)
 track (id, cd_id, title, sequence)
Defining Classes
9th
February 2013
45
DBIC Classes
 Two mandatory types of class
 One schema class
− CD::Schema
 One result class for each table
− CD::Schema::Result::Artist
− CD::Schema::Result::CD
− CD::Schema::Result::Track
9th
February 2013
46
Schema Class
 Define schema class
 CD/Schema.pm
 package CD::Schema;
use strict;
use warnings;
use base qw/DBIx::Class::Schema/;
__PACKAGE__->load_namespaces();
1;
9th
February 2013
47
Result Classes
 Need one result class for every table
 Needs to know
− The table name
− The column names
− The primary key
− Relationships to other tables
9th
February 2013
48
Result Classes
 CD/Schema/Result/Artist.pm
 package CD::Schema::Result::Artist;
use base qw/DBIx::Class::Core/;
__PACKAGE__->table('artist');
__PACKAGE__->add_columns( # simple option
qw/ id name /
);
__PACKAGE__->set_primary_key('id');
__PACKAGE__->has_many(
'cds', 'CD::Schema::Result::CD',
'artist_id'
);
1;
9th
February 2013
49
Result Classes
 CD/Schema/Result/CD.pm
 package CD::Schema::Result::CD;
use base qw/DBIx::Class::Core/;
__PACKAGE__->table('cd');
__PACKAGE__->add_columns(
qw/ id artist_id title year /
);
__PACKAGE__->set_primary_key('id');
__PACKAGE__->belongs_to(
'artist', 'CD::Schema::Result::Artist',
'artist_id'
);
__PACKAGE__->has_many(
'tracks', 'CD::Schema::Result::Track', 'cd_id'
);
1;
9th
February 2013
50
Result Classes
 CD/Schema/Result/Track.pm
 package CD::Schema::Result::Track;
use base qw/DBIx::Class::Core/;
__PACKAGE__->table('track');
__PACKAGE__->add_columns(
qw/ id cd_id title sequence /
);
__PACKAGE__->set_primary_key('id');
__PACKAGE__->belongs_to(
'cd', 'CD::Schema::Result::CD', 'cd_id'
);
1;
9th
February 2013
51
Defining Columns
 At a minimum you must define column
names
 But you can give more information
 __PACKAGE__->add_columns(
id => {
data_type => 'integer',
is_auto_increment => 1,
},
name => {
data_type => 'varchar',
size => 255,
}
);
9th
February 2013
52
Defining Relationships
 We have seen has_many and belongs_to
 Both ends of a many-to-one relationship
 Most common type of relationship
 Artists to CDs
 CDs to tracks
 Manager to employees
 Invoice to invoice lines
 Simple foreign key relationship
9th
February 2013
53
Other Relationships
 has_one
− Only one child record
− Person has one home address
 might_have
− Optional has_one relationship
 Affects the SQL that is generated
9th
February 2013
54
Don't Repeat Yourself
 The Pragmatic Programmer says “Don't
repeat yourself”
 Only one source for every piece of
information
 We are breaking this rule
 We have repeated data
9th
February 2013
55
Repeated Information
 CREATE TABLE artist (
artistid INTEGER PRIMARY KEY,
name TEXT NOT NULL
);
9th
February 2013
56
Repeated Information
 package CD::Schema::Result::Artist;
use base qw/DBIx::Class::Core/;
__PACKAGE__->table('artist');
__PACKAGE__->add_columns( # simple option
qw/ id name /
);
__PACKAGE__->set_primary_key('id');
__PACKAGE__->has_many(
'cds', 'CD::Schema::Result::CD',
'artist_id'
);
1;
9th
February 2013
57
Don't Repeat Yourself
 Information is repeated
 Columns and relationships defined in the
database schema
 Columns and relationships defined in class
definitions
9th
February 2013
58
Don't Repeat Yourself
 Need to define one canonical representation
for data definitions
 Generate the other one
 Let's choose the DDL
 Generate the classes from the DDL
9th
February 2013
59
Database Metadata
 Some people don't put enough metadata in
their databases
 Just tables and columns
 No relationships. No constraints
 You may as well make each column
VARCHAR(255)
9th
February 2013
60
Database Metadata
 Describe your data in your database
 It's what your database is for
 It's what your database does best
9th
February 2013
61
DBIC::Schema::Loader
 DBIx::Class::Schema::Loader
− Separate distribution on CPAN
 Creates classes by querying your database
metadata
 No more repeated data
 We are now DRY
 Schema definitions in one place
9th
February 2013
62
dbicdump
 DBIC::Schema::Loader comes with a
command line program called dbicdump
 $ dbicdump CD::Schema dbi:mysql:database=cd root ''
Dumping manual schema for CD::Schema to
directory . ...
Schema dump completed.
 $ find CD
CD
CD/Schema
CD/Schema/Result
CD/Schema/Result/Cd.pm
CD/Schema/Result/Artist.pm
CD/Schema/Result/Track.pm
CD/Schema.pm
Simple CRUD
9th
February 2013
Loading DBIC Libraries
 Load the main schema class
 use CD::Schema;
 The load_namespaces call takes care of
loading the rest of the classes
9th
February 2013
Connecting to DB
 The DBIC equivalent of a database handle is
called a schema
 Get one by calling the connect method
 my $sch = CD::Schema->connect(
'dbi:mysql:database=cd', $user, $pass
);
 Connection parameters passed through to
DBI
9th
February 2013
Inserting Data
 Interact with tables using a resultset object
 The schema class has a resultset method that
will give you a resultset object
 my $art_rs = $sch->resultset('Artist');
9th
February 2013
Inserting Artists
 Use the create method on a resultset to insert
data into a table
 my @artists = ('Elbow',
'Arcade Fire');
foreach (@artists) {
$art_rs->create({ name => $_ });
}
 Pass a hash reference containing data
 Handles auto-increment columns
9th
February 2013
Inserting Artists
 The create method returns a new artist
object
− Actually a CD::Schema::Result::Artist
 my $bowie = $art_rs->create({
name => 'David Bowie'
});
 Result objects have methods for each
column
 say $bowie->id;
9th
February 2013
Inserting Artists
 An alternative is to use the populate()
method
 my @artists = $art_rs->populate(
[ 'name' ],
[ 'Arcade Fire' ],
[ 'Elbow' ],
);
 Pass one array reference for each row
 First argument is a list of column names
9th
February 2013
Insert Related Records
 Easy to insert objects related to existing
objects
 $bowie->add_to_cds({
title => 'The Next Day',
year => 2013
});
 Foreign key added automatically
 add_to_cds method added because of
relationships
9th
February 2013
Reading Data
 Selecting data is also done through a
resultset object
 We use the search() method
 my ($bowie) = $art_rs->search({
name => 'David Bowie'
});
9th
February 2013
Reading Data
 There's also a find() method
 Use when you know there's only one
matching row
 For example, using primary key
 my $bowie = $art_rs->find({
id => 3,
});
 my $bowie = $art_rs->find(3);
9th
February 2013
Searching Relationships
 Defining relationships allows us to move
from object to object easily
 my $cd_rs = $sch->resultset('CD');
my ($cd) = $cd_rs->search({
title => 'The Seldom Seen Kid'
});
say $cd->artist->name; # Elbow
 The artist() method returns the associated
artist object
9th
February 2013
Searching Relationships
 This works the other way too
 my ($artist) = $art_rs->search({
name => 'Elbow',
});
foreach ($artist->cds) {
say $_->title;
}
 The cds() method returns the associated CD
objects
9th
February 2013
75
What Search Returns
 The search() method returns different things
in different contexts
 In list context it returns a list of result
objects that it has found
 In scalar context it returns another resultset
− That only contains the matching result objects
9th
February 2013
76
What Search Returns
 my $artist = $art_rs->search({
name => 'Elbow';
});
− $artist is a resultset object
 my ($artist) = $art_rs->search({
name => 'Elbow';
});
− $artist is a result object
9th
February 2013
77
Taming Search
 To get all of the result objects from a
resultset call its all() method
 my $artist = $art_rs->search({
name => 'Elbow';
})->all;
− $artist is a result object
9th
February 2013
78
Taming Search
 To get always get a resultset, use search_rs()
instead of search()
 my ($artist) = $art_rs->search_rs({
name => 'Elbow';
});
− $artist is a resultset object
9th
February 2013
Updating Data
 Once you have a result object you can
change any of its attributes
 $bowie->name('Thin White Duke');
 Use the update() method to save it to the
database
 $bowie->update();
9th
February 2013
Updating Data
 You can also call update() on a resultset
 my $davids = $art_rs->search({
name => { like => 'David %' },
});
$davids->update({
name => 'Dave',
});
9th
February 2013
Deleting Data
 Deleting works a lot like updating
 Delete a single record
 my ($britney) = $art_rs->search({
name => 'Britney Spears'
});
$britney->delete;
9th
February 2013
Deleting Data
 You can also delete a resultset
 my $cliffs = $art_rs->search({
name => { like => 'Cliff %' }
});
$cliffs->delete;
9th
February 2013
Cascading Deletes
 What if any of the artists have CDs in the
database?
 They get deleted too
 Referential integrity
 Prevent this by changing relationship
definition
 __PACKAGE__->has_many(
'cds', 'CD::Schema::Result::CD', 'artistid',
{ cascade_delete => 0 },
);
9th
February 2013
Insert Multiple Records
 Create can be used to insert many rows
 $art_rs->create({
name => 'Arcade Fire',
cds => [{
title => 'The Suburbs'
},
{
title => 'Funeral'
}]
});
9th
February 2013
Find or Insert
 Insert an object or return an existing one
 my $killers = $art_rs->find_or_create({
name => 'The Killers'
});
 Note: Need a unique index on one of the
search columns
9th
February 2013
Update or Create
 Update an existing object or create a new
one
 my $killers = $art_rs->update_or_create({
name => 'The Killers'
});
 Note: Need a unique index on one of the
search columns
9th
February 2013
Transactions
 Transactions protect the referential integrity
of your data
 Chunk of work that must all happen
 Temporary workspace for DB changes
 Commit or rollback at the end
9th
February 2013
Transactions & DBIC
 Schema object has a txn_do() method
 Takes a code reference as a parameter
 Adds BEGIN and COMMIT (or
ROLLBACK) around code
 Transactions can include Perl code
9th
February 2013
Transactions & DBIC
 $schema->txn_do( sub {
my $obj = $rs->create(%some_obj);
$obj->add_to_children(%some_child);
});
Advanced Searches
9th
February 2013
Advanced Searches
 search() can be used for more complex
searchs
 See SQL::Abstract documentation for full
details
9th
February 2013
AND
 Use a hash reference to combine conditions
using AND
 $person_rs->search({
forename => 'Dave',
email => 'dave@perlschool.co.uk'
});
 WHERE forename = 'Dave'
AND email = 'dave@perlschool.co.uk'
9th
February 2013
OR
 Use an array reference to combine
conditions using OR
 $person_rs->search([{
forename => 'Dave'
}, {
email => 'dave@perlschool.co.uk'
}]);
 WHERE forename = 'Dave'
OR email = 'dave@perlschool.co.uk'
9th
February 2013
Combinations
 Combine hash references and array
references for more flexibility
 $person_rs->search([{
forename => 'Dave',
username => 'dave'
}, {
email = 'dave@perlschool.co.uk'
}]);
9th
February 2013
Many Values for Column
 Use an array reference to test many values
for a column
 $person_rs->search({
forename => [ 'Dave', 'David' ]
});
 WHERE forename = 'Dave'
OR forename = 'David'
9th
February 2013
Using SQL
 SQL::Abstract supports some SQL options
 $person_rs->search({
forename => { like => 'Dav%' }
});
 WHERE forename LIKE 'Dav%'
9th
February 2013
Using SQL
 More SQL-like options
 $person_rs->search({
forename => {
'-in' => [ 'Dave', 'David' ]
}
});
 WHERE forename IN ('Dave', 'David')
9th
February 2013
Using SQL
 More SQL-like options
 $person_rs->search({
birth_year => {
'-between' => [ 1970, 1980 ]
}
});
 WHERE birth_year
BETWEEN 1970 AND 1980
9th
February 2013
Extra Search Attributes
 All of our examples have used one
parameter to search
 $rs->search(%where_clause)
 Search takes an optional second parameter
 Defines search attributes
 $rs->search(%where_clause, %attrs)
9th
February 2013
Select Specific Columns
 Default search selects all columns in a table
− Actually all attributes in the class
 Use the columns attribute to change this
 $person_rs->search({
forename => 'Dave'
}, {
columns => [ 'me.forename',
'me.surname' ]
});
 Note table aliases
9th
February 2013
Add Columns
 You can invent columns and add them to the
returned object
 $person_rs->search({
forename => 'Dave'
}, {
+columns => {
namelen => { length => 'me.forename' }
}
});
 Use get_column() to access this data
 $person->get_column('namelen')
9th
February 2013
Ordering Data
 Use search attributes to order the data
 $person_rs->search({
forename => 'Dave'
}, {
order => { '-asc' =>
[ 'me.surname' ] }
});
9th
February 2013
Paging
 Select a subset of the data
 $person_rs->search({
forename => 'Dave',
}, {
rows => 10,
page => 2
});
 You probably want to sort that query
9th
February 2013
Joining Tables
 Use the join attribute to join to other tables
 $art_rs->search({}, {
columns => [ 'me.name', 'cds.title' ],
join => [ 'cds' ]
});
 Join artist table to CD table
 Return artist name and CD title
9th
February 2013
Aggregate Functions
 Use SQL aggregate functions like COUNT,
SUM and AVERAGE
 $person_rs->search({}, {
columns => [ 'me.forename',
name_count => {
count => 'me.forename'
} ],
group_by => [ 'me.forename' ]
});
 Use get_columns() to get the count
9th
February 2013
Join and Aggregate
 Combine joins and aggregates
 $art_rs->search({}, {
columns => [ 'me.name',
cd_count => {
count => 'cds.id'
} ],
group_by => [ 'me.forename' ],
join => [ 'cds' ]
});
9th
February 2013
Chaining Resultsets
 We said that search() can return a resultset
 We can call search() again on that resultset
to further specify the search
 And so on...
9th
February 2013
Chaining Resultsets
 my $daves = $person_rs->search({
forename => 'Dave'
});
my $women => $daves_rs->search({
sex => 'F'
});
foreach ($women->all) {
say $_->forename, ' ', $_->surname;
}
9th
February 2013
Executing Resultsets
 A resultset is the definition of a query
 The query isn't run until you execute the
resultset
 By calling all(), first(), next(), etc
− $person_rs->all
 By calling search() in list context
− @daves = $person_rs->search({
forename => 'Dave',
});
More on Result Classes
9th
February 2013
Result Classes
 Result classes are usually generated by
DBIx::Class::Schema::Loader
 Define columns
 Define relationships
 But we can add our own code to these
classes
9th
February 2013
112
Derived Columns
 Sometimes it's handy to have a “column”
that is derived from other columns
 Just add a method
 sub name {
my $self = shift;
return $self->forename, ' ',
$self->surname;
}
9th
February 2013
113
Actions
 Add methods defining actions that your class
needs to carry out
 sub marry {
my $self = shift;
my $spouse = shift;
$self->spouse($spouse->id);
$spouse->spouse($self->id);
}
9th
February 2013
114
Column Inflation
 Inflate a column into a more useful class
when reading from database
 Deflate object into string before saving to
database
 e.g. Convert datetime column to DateTime
object
9th
February 2013
115
DateTime Inflation
 This is a standard feature of DBIC
 DBIx::Class::InflateColumn::DateTime
 Load as a component
− __PACKAGE__->load_component(
'DBIx::Class::InflateColumn::DateTime'
);
 Define column as datetime
− __PACKAGE__->add_columns(
birth => { datatype => 'datetime' }
);
9th
February 2013
116
DateTime Inflation
 my $person = $person_rs->first;
my $birth = $person->birth;
say ref $birth; # DateTime
say $birth->day_name;
 $person_rs->create({
name => 'Some Person',
birth => DateTime->now
});
9th
February 2013
117
DBIC::Schema::Loader
 Use the -o command line option to include
components in generated classes
 dbicdump -o
components='[“InflateColumn::DateTime”]'
...
 Adds the load_components() call to the
classes
9th
February 2013
118
Manual Inflation
 You can define your own inflation/deflation
code
 Use the inflate_column() method
 __PACKAGE__->inflate_column(
'column_name' => {
inflate_column => sub { ... },
deflate_column => sub { ... },
}
);
9th
February 2013
119
Unicode Inflation
 Databases store strings as a series of bytes
 Well-behaved Unicode-aware code converts
bytes to characters as the string enters the
program
− And vice versa
 Many DBDs have a flag to do this
automatically
 Some don't
9th
February 2013
120
Unicode Inflation
 use Encode;
__PACKAGE__->inflate_column(
'some_text_column' => {
inflate_column => sub {
return decode('utf8', $_[0]);
},
deflate_column => sub {
return encode('utf8', $_[0]);
},
}
);
9th
February 2013
121
Relationships
 DBIx::Class::Schema::Loader generates
many kinds of relationships from metadata
 It doesn't recognise many-to-many
relationships
− Linking tables
 We can add them manually in the result
class
9th
February 2013
122
Many to Many
 An actor appears in many films
 A film features many actors
 How do you model that relationship?
 Add a linking table
− Appearance
 Two foreign keys
9th
February 2013
123
Many to Many
9th
February 2013
124
Many to Many
 DBIx::Class::Schema::Loader finds the
standard relationships
− Actor has many Appearances
− Appearances belong to Actor
− Film has many Appearances
− Appearances belong to Film
 We can add a many to many relationship
− In both directions
9th
February 2013
Many to Many
 Film::Schema::Result::Actor->many_to_many(
'films', # new relationship name
'appearances', # linking relationship
'film' # FK relationship in link table
);
Film::Schema::Result::Film->many_to_many(
'actors', # new relationship name
'appearances', # linking relationship
'actor', # FK relationship in link table
);
9th
February 2013
Without Many to Many
 my $depp = $actor_rs->search({
name => 'Johnny Depp'
});
foreach ($depp->appearances) {
say $_->film->title;
}
9th
February 2013
With Many to Many
 my $depp = $actor_rs->search({
name => 'Johnny Depp'
});
foreach ($depp->films) {
say $_->title;
}
9th
February 2013
Editing Result Classes
 Editing result classes is useful
 But result classes are usually generated
− DBIx::Class::Schema::Loader
 How do we regenerate classes?
 Without overwriting our additions
9th
February 2013
MD5 Hash
 A generated result class contains an MD5
hash
 # Created by DBIx::Class::Schema::Loader
v0.05003 @ 2010-04-04 13:53:54
# DO NOT MODIFY THIS OR ANYTHING ABOVE!
md5sum:IvAzC9/WLrHifAi0APmuRw
 Add anything below this line
 Code below this line is preserved on
regeneration
9th
February 2013
Resultset Classes
 We've looked a lot at editing result classes
 You can also edit resultset classes
 Often to add new search methods
 But resultset classes don't exist as files
 Need to create them first
9th
February 2013
Resultset Class
 package App::Schema::Resultset::Person
use strict;
use warnings;
use base 'DBIx::Class::Resultset';
1;
9th
February 2013
Default Search Values
 sub search_men {
my $self = shift;
return $self->search({
sex => 'M'
});
}
9th
February 2013
Default Search Values
 sub search_men {
my $self = shift;
my ($cols, $opts) = @_;
$cols ||= {};
$opts ||= {};
$cols->{sex} = 'M';
return $self->search(
$cols, $opts
);
}
9th
February 2013
Default Search Options
 sub search_sorted {
my $self = shift;
return $self->search({}, {
order_by => 'name ASC'
});
}
 Similar changes for full version
Extending DBIC
9th
February 2013
136
Extending DBIC
 DBIC is powerful and flexible
 Most of the time it can be made to do what
you want
 Sometimes you need to change its default
behaviour
 Override default methods
9th
February 2013
137
Overriding Methods
 Overriding methods is a standard OO
technique
 Method in a subclass replaces one in a
superclass
 Define subclass method with same name
 Subclass method has new behaviour
9th
February 2013
138
Overriding Methods
 Often the subclass behaviour needs to
happen in addition to the superclass
behaviour
 Subclass method needs to call the superclass
method
 Ugly syntax
 $self->SUPER::method()
9th
February 2013
139
Overriding Methods
 sub do_something {
my $self = shift;
...
$self->SUPER::do_something(@_);
...
}
9th
February 2013
140
Class::C3 / mro
 DBIC uses a non-standard method
resolution technique
 mro
− Method resolution order
 Specifically its Class::C3 implementation
 “better consistency in multiple inheritance
situations”
9th
February 2013
141
Class::C3 / mro
 All you really need to know
 When overloading DBIC methods, use
$self->next::method instead of SUPER
 sub do_something {
my $self = shift;
...
$self->next::method(@_);
...
}
9th
February 2013
142
Overriding new()
 Result classes don't include a new method
 That's defined in the DBIx::Class superclass
 We can override it
 sub new {
my $class = shift;
# do stuff
return $self->next::method(@_);
}
9th
February 2013
143
Overriding new()
 Defaults for missing attributes
 sub new {
my $class = shift;
my $obj = shift;
# Set birthday if it's missing
$obj->{birth} ||= DateTime->now;
# Superclass method does real work
return $self->next::method($obj);
}
9th
February 2013
144
Overriding update()
 Add audit information
 sub update {
my $self = shift;
# Set audit columns
$self->upd_time(DateTime->now);
$self->upd_by($Curr_User);
# Superclass method does real work
$self->next::method();
say $self->name, ' updated';
}
9th
February 2013
145
Overriding delete()
 Don't really delete rows
 sub delete {
my $self = shift;
# Set deleted flag
$self->deleted(1);
# Don't call superclass method!
$self->update;
}
9th
February 2013
146
DBIC and Moose
 Moose is the future of OO Perl
 Moose makes OO Perl easier, more
powerful and more flexible
 Moose supports use alongside non-Moose
classes
− MooseX::NonMoose
 We can use DBIC with Moose
9th
February 2013
147
Write Your Own Classes
 package CD::Schema::Result::Artist;
use Moose;
use MooseX::NonMoose;
extends 'DBIx::Class:Core';
__PACKAGE__->table('artist');
__PACKAGE__->add_columns(...);
__PACKAGE__->set_primary_key(...);
# define relationships
...
__PACKAGE__->meta->make_immutable;
9th
February 2013
148
Write Your Own Classes
 package CD::Schema::Result::Artist;
use Moose;
use MooseX::NonMoose;
extends 'DBIx::Class:Core';
__PACKAGE__->table('artist');
__PACKAGE__->add_columns(...);
__PACKAGE__->set_primary_key(...);
# define relationships
...
__PACKAGE__->meta->make_immutable;
9th
February 2013
149
Using Moose Class
 As far as the user (i.e. the application
programmer) is concerned there is no
difference
 The same code will work
 my $artist_rs = $schema->resultset('Artist');
 my $artist = $art_rs->create(%artist);
 $artist->update;
 $artist_rs->search();
9th
February 2013
150
Using Moose Class
 For the programmer writing the class, life
gets better
 We now have all of the power of Moose
 Particularly for overriding methods
 Method modifiers
9th
February 2013
151
Method Modifiers
 More flexible and powerful syntax for
overriding methods
 More control over interaction between
subclass method and superclass method
 Easier syntax
− No $self->SUPER::something()
− No $self->next::method()
9th
February 2013
152
Overriding new()
 Run subclass method before superclass
method
 before new => sub {
my $class = shift;
my $obj = shift;
# Set birthday if it's missing
$obj->{birth} ||= DateTime->now;
# Superclass method run
# automatically
}
9th
February 2013
153
Overriding update()
 Run subclass method around superclass
method
 around update => sub {
my $orig = shift;
my $self = shift;
# Set audit columns
$self->upd_time(DateTime->now);
$self->upd_by($Curr_User);
# Superclass method does real work
$self->$orig(@_);
say $self->name, ' updated';
}
9th
February 2013
154
Overriding delete()
 Run subclass method in place of superclass
method
 override delete => sub {
my $self = shift;
# Set deleted flag
$self->deleted(1);
# Don't call superclass method!
$self->update;
}
9th
February 2013
155
Adding Roles
 Moose roles are pre-packaged features that
can be added into your class
 Like mixins or interfaces in other OO
languages
 Added with the keyword “with”
9th
February 2013
156
Role Example
 package App::Schema::Result::SomeTable;
use Moose;
use MooseX::NonMoose;
extends 'DBIx::Class::Core';
with 'Some::Clever::Role';
9th
February 2013
157
DBIC::Schema::Loader
 DBIx::Class::Schema::Loader has built-in
support for Moose
 use_moose option
 With dbicdump
 $ dbicdump -o use_moose=1 CD::Schema 
dbi:mysql:database=cd root ''
 Creates classes with the Moose lines
included
Deploying Schemas
9th
February 2013
Changing Schemas
 Database schemas change over time
 Tables added
 Columns added
 Column definitions change
 DBIC has tools to manage that
9th
February 2013
Don't Repeat Yourself
 We have two definitions of our database
schema
 DDL
− CREATE TABLE, etc
 DBIC
− Perl code
 Choose one as canonical source
9th
February 2013
DDL vs DBIC
 We can create DBIC code from DDL
− DBIx::Class::Schema::Loader
 We can create DDL from DBIC
− $schema->deploy()
9th
February 2013
Deploy
 Schema objects have a deploy() method
 Generates DDL
− Using SQL::Translator
− Applies it to connected database
 Can also see the DDL
− deployment_statements()
− create_ddl_dir()
9th
February 2013
Schema Versions
 Versions change over time
 Need to cope with that
 Add a version to our schema class
 Set $VERSION
9th
February 2013
Schema Versions
 package CD::Schema;
use warnings;
use strict;
use base 'DBIx::Class::Schema';
our $VERSION = '0.01';
__PACKAGE__->load_namespaces();
1;
9th
February 2013
Schema Versions
 package CD::Schema;
use warnings;
use strict;
use base 'DBIx::Class::Schema';
our $VERSION = '0.01';
__PACKAGE__->load_namespaces();
1;
9th
February 2013
create_ddl_dir
 The create_ddl_dir() method is clever
 Given a previous version of a schema
 It can create ALTER TABLE statements
 $schema->create_ddl_dir(
[ 'MySQL' ], $curr_ver,
$directory, $preversion
);
 This will be very useful
9th
February 2013
Deploying Versions
 DBIC includes a module called
DBIx::Class::Schema::Versioned
 Upgrades schemas
9th
February 2013
DBIC::Sch::Versioned
 More changes to your schema class
 package MyApp::Schema;
use base qw/DBIx::Class::Schema/;
our $VERSION = 0.001;
__PACKAGE__->load_namespaces;
__PACKAGE__->load_components(
qw/Schema::Versioned/
);
__PACKAGE__->upgrade_directory(
'/path/to/upgrades/'
);
9th
February 2013
DBIC::Sch::Versioned
 More changes to your schema class
 package MyApp::Schema;
use base qw/DBIx::Class::Schema/;
our $VERSION = 0.001;
__PACKAGE__->load_namespaces;
__PACKAGE__->load_components(
qw/Schema::Versioned/
);
__PACKAGE__->upgrade_directory(
'/path/to/upgrades/'
);
9th
February 2013
Create Upgrade DDL
 use Getopt::Long;
use CD::Schema;
my $preversion, $help;
GetOptions(
'p|preversion:s' => $preversion,
) or die;
my $schema = MyApp::Schema->connect(...);
# continued...
9th
February 2013
Create Upgrade DDL
 my $sql_dir = './sql';
 my $version = $schema->schema_version();
 $schema->create_ddl_dir(
'MySQL', $version, $sql_dir,
$preversion
);
 Creates all the DDL you need
− Includes versioning tables
9th
February 2013
Upgrade DB
 use CD::Schema;
my $schema = CD::Schema->connect(...);
if ($schema->get_db_version()) {
# Runs all the upgrade SQL
$schema->upgrade();
} else {
# Schema is unversioned
# Installs empty tables
$schema->deploy();
}
9th
February 2013
Better Tool
 DBIC::Schema::Versioned is part of the
standard DBIC package
 DBIC::DeploymentHandler is a separate
CPAN package
 More powerful
 More flexible
9th
February 2013
DBIC::DeploymentHndlr
 Advantages
− Upgrades and downgrades
− Multiple SQL files in one upgrade
− Use Perl scripts for upgrade
 Disadvantages
− Dependency hell
Replication
9th
February 2013
Replication
 Some databases allow multiple copies of the
same data
 Server software keeps replicants in step
 This can aid performance
 Different clients can talk to different servers
 Data on some replicants can lag
9th
February 2013
Types of Replication
 Master-Slave
− One writeable copy of the database
− Many readable replicants
− e.g. MySQL
9th
February 2013
Types of Replication
 Multiple Master
− Many writeable copies
− Potential for deadlocks
− e.g. Sybase
9th
February 2013
DBIC & Replication
 DBIC has beta support for master/slave
replication
 Directs all writes to master connection
 Directs all reads to slave connection
9th
February 2013
DBIC & Replication
 Set the storage_type attribute on our schema
object
 my $schema = CD::Schema->connect(...);
$schema->storage_type([
'::DBI::Replicated',
{ balancer => 'Random' },
]);
9th
February 2013
Add Slaves
 Add slave connections
 $schema->storage->connect_replicants(
[$dsn1, $user, $pass, %opts],
[$dsn2, $user, $pass, %opts],
[$dsn3, $user, $pass, %opts],
);
9th
February 2013
Use Schema
 Use schema as usual
 Reads are delegated to a random slave
 Writes are delegated to the master
 You can force a read to the master
 $rs->search({ ... },
{ force_pool => 'master' });
− Avoid race conditions
Further Information
9th
February 2013
Documentation
 Lots of good DBIC documentation
− perldoc DBIx::Class
− perldoc DBIx::Class::Manual
 DBIx::Class::Manual::SQLHackers
− Separate documentation distribution
9th
February 2013
Support
 Web site
− http://www.dbix-class.org/
 Mailing list
− See support page on web site
 IRC channel
− #dbix-class on irc.perl.org
9th
February 2013
Books
 Good coverage in The Definitive Guide to
Catalyst
− Not completely up to date
 DBIC book being written
− Schedule unknown
That's All Folks
• Any Questions?
• Any Questions?

More Related Content

What's hot

1.2.2 incorporando sentencias dml y funciones sql a bloques plsql
1.2.2 incorporando sentencias dml y funciones sql a bloques plsql1.2.2 incorporando sentencias dml y funciones sql a bloques plsql
1.2.2 incorporando sentencias dml y funciones sql a bloques plsql
Ricardo Riquelme Pinto
 
Mengenal DDL, DML dan DCL dalam DATABASE.pptx
Mengenal DDL, DML dan DCL dalam DATABASE.pptxMengenal DDL, DML dan DCL dalam DATABASE.pptx
Mengenal DDL, DML dan DCL dalam DATABASE.pptx
MuhammadLutfi611209
 
MySQL for beginners
MySQL for beginnersMySQL for beginners
MySQL for beginners
Saeid Zebardast
 
Clean code slide
Clean code slideClean code slide
Clean code slide
Anh Huan Miu
 
Laporan Praktikum Basis Data Modul VI-Membuat Website
Laporan Praktikum Basis Data Modul VI-Membuat WebsiteLaporan Praktikum Basis Data Modul VI-Membuat Website
Laporan Praktikum Basis Data Modul VI-Membuat Website
Shofura Kamal
 
Basic Sql Handouts
Basic Sql HandoutsBasic Sql Handouts
Basic Sql Handouts
jhe04
 
[PBO] Pertemuan 4 - Getter Setter
[PBO] Pertemuan 4 - Getter Setter[PBO] Pertemuan 4 - Getter Setter
[PBO] Pertemuan 4 - Getter Setter
rizki adam kurniawan
 
Clean code: meaningful Name
Clean code: meaningful NameClean code: meaningful Name
Clean code: meaningful Name
nahid035
 
Encapsulamento em Orientação a Objetos
Encapsulamento em Orientação a ObjetosEncapsulamento em Orientação a Objetos
Encapsulamento em Orientação a Objetos
Daniel Brandão
 
Mysql ppt
Mysql pptMysql ppt
Mysql ppt
Sanmuga Nathan
 
Stored procedure
Stored procedureStored procedure
8 Data Record
8 Data Record8 Data Record
8 Data Record
Simon Patabang
 
PHP 5.3 - Funções
PHP 5.3 - FunçõesPHP 5.3 - Funções
PHP 5.3 - Funções
George Mendonça
 
Program memasukan data barang dengan php mysql
Program memasukan data barang dengan php mysqlProgram memasukan data barang dengan php mysql
Program memasukan data barang dengan php mysql
Universitas Komputer Indonesia
 
Php Basico
Php BasicoPhp Basico
Php Basico
Eliecer Cedano
 
SQL
SQLSQL
Sql – Structured Query Language
Sql – Structured Query LanguageSql – Structured Query Language
Sql – Structured Query Language
pandey3045_bit
 
Function dalam PHP
Function dalam PHPFunction dalam PHP
Function dalam PHP
I Gede Iwan Sudipa
 

What's hot (20)

1.2.2 incorporando sentencias dml y funciones sql a bloques plsql
1.2.2 incorporando sentencias dml y funciones sql a bloques plsql1.2.2 incorporando sentencias dml y funciones sql a bloques plsql
1.2.2 incorporando sentencias dml y funciones sql a bloques plsql
 
Os2013 lap2-ridwan
Os2013 lap2-ridwanOs2013 lap2-ridwan
Os2013 lap2-ridwan
 
Mengenal DDL, DML dan DCL dalam DATABASE.pptx
Mengenal DDL, DML dan DCL dalam DATABASE.pptxMengenal DDL, DML dan DCL dalam DATABASE.pptx
Mengenal DDL, DML dan DCL dalam DATABASE.pptx
 
MySQL for beginners
MySQL for beginnersMySQL for beginners
MySQL for beginners
 
Clean code slide
Clean code slideClean code slide
Clean code slide
 
Laporan Praktikum Basis Data Modul VI-Membuat Website
Laporan Praktikum Basis Data Modul VI-Membuat WebsiteLaporan Praktikum Basis Data Modul VI-Membuat Website
Laporan Praktikum Basis Data Modul VI-Membuat Website
 
Basic Sql Handouts
Basic Sql HandoutsBasic Sql Handouts
Basic Sql Handouts
 
[PBO] Pertemuan 4 - Getter Setter
[PBO] Pertemuan 4 - Getter Setter[PBO] Pertemuan 4 - Getter Setter
[PBO] Pertemuan 4 - Getter Setter
 
Clean code: meaningful Name
Clean code: meaningful NameClean code: meaningful Name
Clean code: meaningful Name
 
Encapsulamento em Orientação a Objetos
Encapsulamento em Orientação a ObjetosEncapsulamento em Orientação a Objetos
Encapsulamento em Orientação a Objetos
 
Mysql ppt
Mysql pptMysql ppt
Mysql ppt
 
Stored procedure
Stored procedureStored procedure
Stored procedure
 
Array dan fungsi
Array dan fungsiArray dan fungsi
Array dan fungsi
 
8 Data Record
8 Data Record8 Data Record
8 Data Record
 
PHP 5.3 - Funções
PHP 5.3 - FunçõesPHP 5.3 - Funções
PHP 5.3 - Funções
 
Program memasukan data barang dengan php mysql
Program memasukan data barang dengan php mysqlProgram memasukan data barang dengan php mysql
Program memasukan data barang dengan php mysql
 
Php Basico
Php BasicoPhp Basico
Php Basico
 
SQL
SQLSQL
SQL
 
Sql – Structured Query Language
Sql – Structured Query LanguageSql – Structured Query Language
Sql – Structured Query Language
 
Function dalam PHP
Function dalam PHPFunction dalam PHP
Function dalam PHP
 

Viewers also liked

Working with databases in Perl
Working with databases in PerlWorking with databases in Perl
Working with databases in Perl
Laurent Dami
 
Working with databases
Working with databasesWorking with databases
Efficient Shared Data in Perl
Efficient Shared Data in PerlEfficient Shared Data in Perl
Efficient Shared Data in Perl
Perrin Harkins
 
DBI Advanced Tutorial 2007
DBI Advanced Tutorial 2007DBI Advanced Tutorial 2007
DBI Advanced Tutorial 2007
Tim Bunce
 
perl usage at database applications
perl usage at database applicationsperl usage at database applications
perl usage at database applications
Joe Jiang
 
Perl Introduction
Perl IntroductionPerl Introduction
Perl Introduction
Marcos Rebelo
 

Viewers also liked (6)

Working with databases in Perl
Working with databases in PerlWorking with databases in Perl
Working with databases in Perl
 
Working with databases
Working with databasesWorking with databases
Working with databases
 
Efficient Shared Data in Perl
Efficient Shared Data in PerlEfficient Shared Data in Perl
Efficient Shared Data in Perl
 
DBI Advanced Tutorial 2007
DBI Advanced Tutorial 2007DBI Advanced Tutorial 2007
DBI Advanced Tutorial 2007
 
perl usage at database applications
perl usage at database applicationsperl usage at database applications
perl usage at database applications
 
Perl Introduction
Perl IntroductionPerl Introduction
Perl Introduction
 

Similar to Database Programming with Perl and DBIx::Class

SQL Complete Tutorial. All Topics Covered
SQL Complete Tutorial. All Topics CoveredSQL Complete Tutorial. All Topics Covered
SQL Complete Tutorial. All Topics Covered
Danish Mehraj
 
RDBMS
RDBMS RDBMS
RDBMS
RamSon Queen
 
DEE 431 Introduction to Mysql Slide 3
DEE 431 Introduction to Mysql Slide 3DEE 431 Introduction to Mysql Slide 3
DEE 431 Introduction to Mysql Slide 3
YOGESH SINGH
 
MongoDB-presentation.pptx
MongoDB-presentation.pptxMongoDB-presentation.pptx
MongoDB-presentation.pptx
tarungupta276841
 
my sql
my sqlmy sql
my sql
Ayush Pandey
 
Mongo db php_shaken_not_stirred_joomlafrappe
Mongo db php_shaken_not_stirred_joomlafrappeMongo db php_shaken_not_stirred_joomlafrappe
Mongo db php_shaken_not_stirred_joomlafrappe
Spyros Passas
 
Exploring Oracle Database 12c Multitenant best practices for your Cloud
Exploring Oracle Database 12c Multitenant best practices for your CloudExploring Oracle Database 12c Multitenant best practices for your Cloud
Exploring Oracle Database 12c Multitenant best practices for your Cloud
dyahalom
 
Big Data Certifications Workshop - 201711 - Introduction and Database Essentials
Big Data Certifications Workshop - 201711 - Introduction and Database EssentialsBig Data Certifications Workshop - 201711 - Introduction and Database Essentials
Big Data Certifications Workshop - 201711 - Introduction and Database Essentials
Durga Gadiraju
 
Unit 3 rdbms study_materials-converted
Unit 3  rdbms study_materials-convertedUnit 3  rdbms study_materials-converted
Unit 3 rdbms study_materials-converted
gayaramesh
 
mongo.pptx
mongo.pptxmongo.pptx
mongo.pptx
tarungupta276841
 
My sql
My sqlMy sql
NoSQL: An Analysis
NoSQL: An AnalysisNoSQL: An Analysis
NoSQL: An Analysis
Andrew Brust
 
Chap09
Chap09Chap09
Jason Olson - IBM i DB2 Modernization to SQL
Jason Olson - IBM i DB2 Modernization to SQLJason Olson - IBM i DB2 Modernization to SQL
Jason Olson - IBM i DB2 Modernization to SQL
John Zozzaro
 
NoSQL Seminer
NoSQL SeminerNoSQL Seminer
NoSQL Seminer
Partha Das
 
Database Systems - Introduction to SQL (Chapter 3/1)
Database Systems - Introduction to SQL (Chapter 3/1)Database Systems - Introduction to SQL (Chapter 3/1)
Database Systems - Introduction to SQL (Chapter 3/1)
Vidyasagar Mundroy
 
Dbms and sqlpptx
Dbms and sqlpptxDbms and sqlpptx
Dbms and sqlpptx
thesupermanreturns
 
Kskv kutch university DBMS unit 1 basic concepts, data,information,database,...
Kskv kutch university DBMS unit 1  basic concepts, data,information,database,...Kskv kutch university DBMS unit 1  basic concepts, data,information,database,...
Kskv kutch university DBMS unit 1 basic concepts, data,information,database,...
Dipen Parmar
 
Introduction to NoSQL with MongoDB
Introduction to NoSQL with MongoDBIntroduction to NoSQL with MongoDB
Introduction to NoSQL with MongoDB
Hector Correa
 
RDBMS
RDBMSRDBMS

Similar to Database Programming with Perl and DBIx::Class (20)

SQL Complete Tutorial. All Topics Covered
SQL Complete Tutorial. All Topics CoveredSQL Complete Tutorial. All Topics Covered
SQL Complete Tutorial. All Topics Covered
 
RDBMS
RDBMS RDBMS
RDBMS
 
DEE 431 Introduction to Mysql Slide 3
DEE 431 Introduction to Mysql Slide 3DEE 431 Introduction to Mysql Slide 3
DEE 431 Introduction to Mysql Slide 3
 
MongoDB-presentation.pptx
MongoDB-presentation.pptxMongoDB-presentation.pptx
MongoDB-presentation.pptx
 
my sql
my sqlmy sql
my sql
 
Mongo db php_shaken_not_stirred_joomlafrappe
Mongo db php_shaken_not_stirred_joomlafrappeMongo db php_shaken_not_stirred_joomlafrappe
Mongo db php_shaken_not_stirred_joomlafrappe
 
Exploring Oracle Database 12c Multitenant best practices for your Cloud
Exploring Oracle Database 12c Multitenant best practices for your CloudExploring Oracle Database 12c Multitenant best practices for your Cloud
Exploring Oracle Database 12c Multitenant best practices for your Cloud
 
Big Data Certifications Workshop - 201711 - Introduction and Database Essentials
Big Data Certifications Workshop - 201711 - Introduction and Database EssentialsBig Data Certifications Workshop - 201711 - Introduction and Database Essentials
Big Data Certifications Workshop - 201711 - Introduction and Database Essentials
 
Unit 3 rdbms study_materials-converted
Unit 3  rdbms study_materials-convertedUnit 3  rdbms study_materials-converted
Unit 3 rdbms study_materials-converted
 
mongo.pptx
mongo.pptxmongo.pptx
mongo.pptx
 
My sql
My sqlMy sql
My sql
 
NoSQL: An Analysis
NoSQL: An AnalysisNoSQL: An Analysis
NoSQL: An Analysis
 
Chap09
Chap09Chap09
Chap09
 
Jason Olson - IBM i DB2 Modernization to SQL
Jason Olson - IBM i DB2 Modernization to SQLJason Olson - IBM i DB2 Modernization to SQL
Jason Olson - IBM i DB2 Modernization to SQL
 
NoSQL Seminer
NoSQL SeminerNoSQL Seminer
NoSQL Seminer
 
Database Systems - Introduction to SQL (Chapter 3/1)
Database Systems - Introduction to SQL (Chapter 3/1)Database Systems - Introduction to SQL (Chapter 3/1)
Database Systems - Introduction to SQL (Chapter 3/1)
 
Dbms and sqlpptx
Dbms and sqlpptxDbms and sqlpptx
Dbms and sqlpptx
 
Kskv kutch university DBMS unit 1 basic concepts, data,information,database,...
Kskv kutch university DBMS unit 1  basic concepts, data,information,database,...Kskv kutch university DBMS unit 1  basic concepts, data,information,database,...
Kskv kutch university DBMS unit 1 basic concepts, data,information,database,...
 
Introduction to NoSQL with MongoDB
Introduction to NoSQL with MongoDBIntroduction to NoSQL with MongoDB
Introduction to NoSQL with MongoDB
 
RDBMS
RDBMSRDBMS
RDBMS
 

More from Dave Cross

Measuring the Quality of Your Perl Code
Measuring the Quality of Your Perl CodeMeasuring the Quality of Your Perl Code
Measuring the Quality of Your Perl Code
Dave Cross
 
Apollo 11 at 50 - A Simple Twitter Bot
Apollo 11 at 50 - A Simple Twitter BotApollo 11 at 50 - A Simple Twitter Bot
Apollo 11 at 50 - A Simple Twitter Bot
Dave Cross
 
Monoliths, Balls of Mud and Silver Bullets
Monoliths, Balls of Mud and Silver BulletsMonoliths, Balls of Mud and Silver Bullets
Monoliths, Balls of Mud and Silver Bullets
Dave Cross
 
The Professional Programmer
The Professional ProgrammerThe Professional Programmer
The Professional Programmer
Dave Cross
 
I'm A Republic (Honest!)
I'm A Republic (Honest!)I'm A Republic (Honest!)
I'm A Republic (Honest!)
Dave Cross
 
Web Site Tune-Up - Improve Your Googlejuice
Web Site Tune-Up - Improve Your GooglejuiceWeb Site Tune-Up - Improve Your Googlejuice
Web Site Tune-Up - Improve Your Googlejuice
Dave Cross
 
Modern Perl Web Development with Dancer
Modern Perl Web Development with DancerModern Perl Web Development with Dancer
Modern Perl Web Development with Dancer
Dave Cross
 
Freeing Tower Bridge
Freeing Tower BridgeFreeing Tower Bridge
Freeing Tower Bridge
Dave Cross
 
Modern Perl Catch-Up
Modern Perl Catch-UpModern Perl Catch-Up
Modern Perl Catch-Up
Dave Cross
 
Error(s) Free Programming
Error(s) Free ProgrammingError(s) Free Programming
Error(s) Free Programming
Dave Cross
 
Medium Perl
Medium PerlMedium Perl
Medium Perl
Dave Cross
 
Modern Web Development with Perl
Modern Web Development with PerlModern Web Development with Perl
Modern Web Development with Perl
Dave Cross
 
Improving Dev Assistant
Improving Dev AssistantImproving Dev Assistant
Improving Dev Assistant
Dave Cross
 
Conference Driven Publishing
Conference Driven PublishingConference Driven Publishing
Conference Driven Publishing
Dave Cross
 
Conference Driven Publishing
Conference Driven PublishingConference Driven Publishing
Conference Driven Publishing
Dave Cross
 
TwittElection
TwittElectionTwittElection
TwittElection
Dave Cross
 
Perl in the Internet of Things
Perl in the Internet of ThingsPerl in the Internet of Things
Perl in the Internet of Things
Dave Cross
 
Return to the Kingdom of the Blind
Return to the Kingdom of the BlindReturn to the Kingdom of the Blind
Return to the Kingdom of the Blind
Dave Cross
 
Github, Travis-CI and Perl
Github, Travis-CI and PerlGithub, Travis-CI and Perl
Github, Travis-CI and Perl
Dave Cross
 
Object-Oriented Programming with Perl and Moose
Object-Oriented Programming with Perl and MooseObject-Oriented Programming with Perl and Moose
Object-Oriented Programming with Perl and Moose
Dave Cross
 

More from Dave Cross (20)

Measuring the Quality of Your Perl Code
Measuring the Quality of Your Perl CodeMeasuring the Quality of Your Perl Code
Measuring the Quality of Your Perl Code
 
Apollo 11 at 50 - A Simple Twitter Bot
Apollo 11 at 50 - A Simple Twitter BotApollo 11 at 50 - A Simple Twitter Bot
Apollo 11 at 50 - A Simple Twitter Bot
 
Monoliths, Balls of Mud and Silver Bullets
Monoliths, Balls of Mud and Silver BulletsMonoliths, Balls of Mud and Silver Bullets
Monoliths, Balls of Mud and Silver Bullets
 
The Professional Programmer
The Professional ProgrammerThe Professional Programmer
The Professional Programmer
 
I'm A Republic (Honest!)
I'm A Republic (Honest!)I'm A Republic (Honest!)
I'm A Republic (Honest!)
 
Web Site Tune-Up - Improve Your Googlejuice
Web Site Tune-Up - Improve Your GooglejuiceWeb Site Tune-Up - Improve Your Googlejuice
Web Site Tune-Up - Improve Your Googlejuice
 
Modern Perl Web Development with Dancer
Modern Perl Web Development with DancerModern Perl Web Development with Dancer
Modern Perl Web Development with Dancer
 
Freeing Tower Bridge
Freeing Tower BridgeFreeing Tower Bridge
Freeing Tower Bridge
 
Modern Perl Catch-Up
Modern Perl Catch-UpModern Perl Catch-Up
Modern Perl Catch-Up
 
Error(s) Free Programming
Error(s) Free ProgrammingError(s) Free Programming
Error(s) Free Programming
 
Medium Perl
Medium PerlMedium Perl
Medium Perl
 
Modern Web Development with Perl
Modern Web Development with PerlModern Web Development with Perl
Modern Web Development with Perl
 
Improving Dev Assistant
Improving Dev AssistantImproving Dev Assistant
Improving Dev Assistant
 
Conference Driven Publishing
Conference Driven PublishingConference Driven Publishing
Conference Driven Publishing
 
Conference Driven Publishing
Conference Driven PublishingConference Driven Publishing
Conference Driven Publishing
 
TwittElection
TwittElectionTwittElection
TwittElection
 
Perl in the Internet of Things
Perl in the Internet of ThingsPerl in the Internet of Things
Perl in the Internet of Things
 
Return to the Kingdom of the Blind
Return to the Kingdom of the BlindReturn to the Kingdom of the Blind
Return to the Kingdom of the Blind
 
Github, Travis-CI and Perl
Github, Travis-CI and PerlGithub, Travis-CI and Perl
Github, Travis-CI and Perl
 
Object-Oriented Programming with Perl and Moose
Object-Oriented Programming with Perl and MooseObject-Oriented Programming with Perl and Moose
Object-Oriented Programming with Perl and Moose
 

Recently uploaded

RESUME BUILDER APPLICATION Project for students
RESUME BUILDER APPLICATION Project for studentsRESUME BUILDER APPLICATION Project for students
RESUME BUILDER APPLICATION Project for students
KAMESHS29
 
Introduction to CHERI technology - Cybersecurity
Introduction to CHERI technology - CybersecurityIntroduction to CHERI technology - Cybersecurity
Introduction to CHERI technology - Cybersecurity
mikeeftimakis1
 
UiPath Test Automation using UiPath Test Suite series, part 5
UiPath Test Automation using UiPath Test Suite series, part 5UiPath Test Automation using UiPath Test Suite series, part 5
UiPath Test Automation using UiPath Test Suite series, part 5
DianaGray10
 
Essentials of Automations: The Art of Triggers and Actions in FME
Essentials of Automations: The Art of Triggers and Actions in FMEEssentials of Automations: The Art of Triggers and Actions in FME
Essentials of Automations: The Art of Triggers and Actions in FME
Safe Software
 
Communications Mining Series - Zero to Hero - Session 1
Communications Mining Series - Zero to Hero - Session 1Communications Mining Series - Zero to Hero - Session 1
Communications Mining Series - Zero to Hero - Session 1
DianaGray10
 
20240609 QFM020 Irresponsible AI Reading List May 2024
20240609 QFM020 Irresponsible AI Reading List May 202420240609 QFM020 Irresponsible AI Reading List May 2024
20240609 QFM020 Irresponsible AI Reading List May 2024
Matthew Sinclair
 
“Building and Scaling AI Applications with the Nx AI Manager,” a Presentation...
“Building and Scaling AI Applications with the Nx AI Manager,” a Presentation...“Building and Scaling AI Applications with the Nx AI Manager,” a Presentation...
“Building and Scaling AI Applications with the Nx AI Manager,” a Presentation...
Edge AI and Vision Alliance
 
Full-RAG: A modern architecture for hyper-personalization
Full-RAG: A modern architecture for hyper-personalizationFull-RAG: A modern architecture for hyper-personalization
Full-RAG: A modern architecture for hyper-personalization
Zilliz
 
Large Language Model (LLM) and it’s Geospatial Applications
Large Language Model (LLM) and it’s Geospatial ApplicationsLarge Language Model (LLM) and it’s Geospatial Applications
Large Language Model (LLM) and it’s Geospatial Applications
Rohit Gautam
 
Removing Uninteresting Bytes in Software Fuzzing
Removing Uninteresting Bytes in Software FuzzingRemoving Uninteresting Bytes in Software Fuzzing
Removing Uninteresting Bytes in Software Fuzzing
Aftab Hussain
 
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdf
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdfUnlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdf
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdf
Malak Abu Hammad
 
Securing your Kubernetes cluster_ a step-by-step guide to success !
Securing your Kubernetes cluster_ a step-by-step guide to success !Securing your Kubernetes cluster_ a step-by-step guide to success !
Securing your Kubernetes cluster_ a step-by-step guide to success !
KatiaHIMEUR1
 
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024
GraphSummit Singapore | The Art of the  Possible with Graph - Q2 2024GraphSummit Singapore | The Art of the  Possible with Graph - Q2 2024
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024
Neo4j
 
Climate Impact of Software Testing at Nordic Testing Days
Climate Impact of Software Testing at Nordic Testing DaysClimate Impact of Software Testing at Nordic Testing Days
Climate Impact of Software Testing at Nordic Testing Days
Kari Kakkonen
 
Generative AI Deep Dive: Advancing from Proof of Concept to Production
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionGenerative AI Deep Dive: Advancing from Proof of Concept to Production
Generative AI Deep Dive: Advancing from Proof of Concept to Production
Aggregage
 
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
名前 です男
 
Artificial Intelligence for XMLDevelopment
Artificial Intelligence for XMLDevelopmentArtificial Intelligence for XMLDevelopment
Artificial Intelligence for XMLDevelopment
Octavian Nadolu
 
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...
James Anderson
 
A tale of scale & speed: How the US Navy is enabling software delivery from l...
A tale of scale & speed: How the US Navy is enabling software delivery from l...A tale of scale & speed: How the US Navy is enabling software delivery from l...
A tale of scale & speed: How the US Navy is enabling software delivery from l...
sonjaschweigert1
 
Presentation of the OECD Artificial Intelligence Review of Germany
Presentation of the OECD Artificial Intelligence Review of GermanyPresentation of the OECD Artificial Intelligence Review of Germany
Presentation of the OECD Artificial Intelligence Review of Germany
innovationoecd
 

Recently uploaded (20)

RESUME BUILDER APPLICATION Project for students
RESUME BUILDER APPLICATION Project for studentsRESUME BUILDER APPLICATION Project for students
RESUME BUILDER APPLICATION Project for students
 
Introduction to CHERI technology - Cybersecurity
Introduction to CHERI technology - CybersecurityIntroduction to CHERI technology - Cybersecurity
Introduction to CHERI technology - Cybersecurity
 
UiPath Test Automation using UiPath Test Suite series, part 5
UiPath Test Automation using UiPath Test Suite series, part 5UiPath Test Automation using UiPath Test Suite series, part 5
UiPath Test Automation using UiPath Test Suite series, part 5
 
Essentials of Automations: The Art of Triggers and Actions in FME
Essentials of Automations: The Art of Triggers and Actions in FMEEssentials of Automations: The Art of Triggers and Actions in FME
Essentials of Automations: The Art of Triggers and Actions in FME
 
Communications Mining Series - Zero to Hero - Session 1
Communications Mining Series - Zero to Hero - Session 1Communications Mining Series - Zero to Hero - Session 1
Communications Mining Series - Zero to Hero - Session 1
 
20240609 QFM020 Irresponsible AI Reading List May 2024
20240609 QFM020 Irresponsible AI Reading List May 202420240609 QFM020 Irresponsible AI Reading List May 2024
20240609 QFM020 Irresponsible AI Reading List May 2024
 
“Building and Scaling AI Applications with the Nx AI Manager,” a Presentation...
“Building and Scaling AI Applications with the Nx AI Manager,” a Presentation...“Building and Scaling AI Applications with the Nx AI Manager,” a Presentation...
“Building and Scaling AI Applications with the Nx AI Manager,” a Presentation...
 
Full-RAG: A modern architecture for hyper-personalization
Full-RAG: A modern architecture for hyper-personalizationFull-RAG: A modern architecture for hyper-personalization
Full-RAG: A modern architecture for hyper-personalization
 
Large Language Model (LLM) and it’s Geospatial Applications
Large Language Model (LLM) and it’s Geospatial ApplicationsLarge Language Model (LLM) and it’s Geospatial Applications
Large Language Model (LLM) and it’s Geospatial Applications
 
Removing Uninteresting Bytes in Software Fuzzing
Removing Uninteresting Bytes in Software FuzzingRemoving Uninteresting Bytes in Software Fuzzing
Removing Uninteresting Bytes in Software Fuzzing
 
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdf
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdfUnlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdf
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdf
 
Securing your Kubernetes cluster_ a step-by-step guide to success !
Securing your Kubernetes cluster_ a step-by-step guide to success !Securing your Kubernetes cluster_ a step-by-step guide to success !
Securing your Kubernetes cluster_ a step-by-step guide to success !
 
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024
GraphSummit Singapore | The Art of the  Possible with Graph - Q2 2024GraphSummit Singapore | The Art of the  Possible with Graph - Q2 2024
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024
 
Climate Impact of Software Testing at Nordic Testing Days
Climate Impact of Software Testing at Nordic Testing DaysClimate Impact of Software Testing at Nordic Testing Days
Climate Impact of Software Testing at Nordic Testing Days
 
Generative AI Deep Dive: Advancing from Proof of Concept to Production
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionGenerative AI Deep Dive: Advancing from Proof of Concept to Production
Generative AI Deep Dive: Advancing from Proof of Concept to Production
 
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
 
Artificial Intelligence for XMLDevelopment
Artificial Intelligence for XMLDevelopmentArtificial Intelligence for XMLDevelopment
Artificial Intelligence for XMLDevelopment
 
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...
 
A tale of scale & speed: How the US Navy is enabling software delivery from l...
A tale of scale & speed: How the US Navy is enabling software delivery from l...A tale of scale & speed: How the US Navy is enabling software delivery from l...
A tale of scale & speed: How the US Navy is enabling software delivery from l...
 
Presentation of the OECD Artificial Intelligence Review of Germany
Presentation of the OECD Artificial Intelligence Review of GermanyPresentation of the OECD Artificial Intelligence Review of Germany
Presentation of the OECD Artificial Intelligence Review of Germany
 

Database Programming with Perl and DBIx::Class

  • 1. Database Programming with Perl and DBIx::Class Dave Cross dave@perlschool.co.uk
  • 2. 9th February 2013 Perl School  Low cost Perl training  Training at all levels  Trying to build a buzz about Perl  Perl is not dead  Perl is Modern
  • 4. 9th February 2013 Your Help Please  Trying to build a buzz about Perl  You can help  Please tell your friends  Blog  Twitter  Facebook  http://perlschool.co.uk
  • 5. 9th February 2013 Upcoming Courses  Perl School 5: Object Oriented Programming with Perl and Moose − 6th April 2013  Perl School 6: Database Programming with Perl and DBIx::Class − 8th June 2013  http://perlschool.co.uk/upcoming/
  • 6. 9th February 2013 Admin Stuff  Tickets  Facilities  Lunch  Slides  Feedback
  • 7. 9th February 2013 Timings  10:00 Session 1  11:15 Break  11:30 Session 2  13:00 Lunch  14:00 Session 3  15:30 Break  15:45 Session 4  17:00 End
  • 8. 9th February 2013 8 What We Will Cover  Introduction to relational databases  Introduction to databases and Perl − DBI − ORM  Schema Classes  Basic DB operations − CRUD
  • 9. 9th February 2013 9 What We Will Cover  Advanced queries − Ordering, joining, grouping  Extending DBIC  Deploying and updating schemas  DBIC and Moose  Further information
  • 11. 9th February 2013 11 Relational Databases  A Relational Model of Data for Large Shared Data Banks − Ted Codd (1970)  Applying relational calculus to databases  See also Chris Date − Database in Depth (2005) − SQL and Relational Theory (2011) − Database Design and Relational Theory (2012)
  • 12. 9th February 2013 12 Relational Concepts  Relation − Table − (Hence “relational”)  Tuple − Row  Attribute − Column
  • 13. 9th February 2013 13 Some More Concepts  Primary key − Unique identifier for a row within a table  Foreign key − Primary key of a table that appears in another table − Used to define relationships between tables − e.g artist_id in a table containing CDs
  • 14. 9th February 2013 14 Referential Integrity  Check that database is in a meaningful state − No CDs without artist ID − No artist IDs that don't exist in the artist table  Constraints that ensure you can't break referential integrity − Don't delete artists that have associated CDs − Don't insert a CD with a non-existent artist ID
  • 15. 9th February 2013 15 SQL  Structured Query Language  Standard language for talking to databases  Invented by IBM early 1970s − SEQUEL  ISO/ANSI standard  Many vendor extensions
  • 16. 9th February 2013 16 DDL & DML  Two sides of SQL  Data Definition Language − Defines tables, etc − CREATE, DROP, etc  Data Manipulation Language − Create, Read, Update, Delete data − CRUD − INSERT, SELECT, UPDATE, DELETE
  • 18. 9th February 2013 18 Talking to Databases  Database vendors supply an API  Usually a C library  Defines functions that run SQL against a DB  All vendors' APIs do the same thing  All vendors' APIs are completely different
  • 19. 9th February 2013 19 Ancient History  Perl 4 had ways to link to external libraries − Like database APIs  Static linking only  Build a separate Perl binary for every database − oraperl, sybperl, etc  Call API functions from Perl code
  • 20. 9th February 2013 20 The Middle Ages  Perl 5 introduced dynamic linking  Load libraries at compile time  Oraperl, Sybperl etc became CPAN modules  use Oraperl;  Still writing DB-specific code
  • 21. 9th February 2013 21 Early Modern Era  DBI.pm  Standard database interface  Database driver converts to API functions − DBD::Oracle, DBD::Sybase, etc  Code becomes more portable  (Except for vendor extensions)
  • 23. 9th February 2013 23 DBI Architecture  Programmer writes code to DBI spec  DBD converts code to database API  DBD converts Perl data structures as appropriate  DBD converts returns data into Perl data structures
  • 24. 9th February 2013 24 Loading DBI  use DBI;  No need to load specific DBD library − Sometimes DBD exports constants that you will need
  • 25. 9th February 2013 25 Connecting to DB  Communicate with database through a “database handle”  my $dbh = DBI->connect( 'dbi:mysql:host=foo.com:database=foo', $username, $password, %options );  Different DBDs have different options  'mysql' defines the DBD to load − DBD::mysql in this case
  • 26. 9th February 2013 26 Selecting Data  Select data using a prepare/execute/fetch cycle  my $sql = 'select col1, col2 from some_tab'; my $sth = $dbh->prepare($sql); $sth->execute; while (my $row = $sth->fetch) { say join ' : ', @$row; }
  • 27. 9th February 2013 27 Inserting Data  Insert data using a similar approach  my $sql = 'insert into some_table (id, col1) values (1, “Foo”)'; my $sth = $dbh->prepare($sql); $sth->execute; # No fetch required  Or using do(...) shortcut  $dbh->do($sql);
  • 28. 9th February 2013 28 Updating and Deleting  Update or delete data in exactly the same way  my $sql = 'update some_table set col1 = “Bar” where id = 1'; my $sth = $dbh->prepare($sql); $sth->execute;  Or  $dbh->do('delete from some_table where id = 1');
  • 29. 9th February 2013 29 DBI Advantages  Standard API for interacting with databases  Programmer no longer needs to understand vendor APIs − Except the DBD author  Increased programmer productivity  Increased programmer flexibility
  • 30. 9th February 2013 30 DBI Disadvantages  Programmers still writing raw SQL − Which is boring − And error-prone  DBI returns “dumb” data structures − Arrays or hashes − Often need to be converted into objects
  • 31. 9th February 2013 31 DB Frameworks  10 years ago people started writing SQL generators  Store a DB row in a hash − DBI has a fetchrow_hashref() method  Generate SQL for simple CRUD operations
  • 32. 9th February 2013 32 Next Steps  Turn those hashes into objects  Class knows table name  Class knows column names  Class knows primary key  SQL generation moved into superclass  All DB tables have an associated class
  • 34. 9th February 2013 34 Relational Database  Consider database storage structures  A table defines a type of data that can be stored  A row is a single instance of that type of data  A column is an attribute of that instance
  • 35. 9th February 2013 35 Object Oriented  Consider OO storage structures  A class defines a type of data that can be stored  An object is a single instance of that type of data  An attribute is an attribute of that instance
  • 36. 9th February 2013 36 ORM  Database concepts and OO concepts map well onto each other  A database table is a lot like an OO class  A database row is a lot like an OO object  A database column is a lot like an OO attribute  We can use this to make our lives easier
  • 37. 9th February 2013 37 ORM Principles  A Object Relational Mapper converts between database data and objects  In both directions  Select data from the database and get an object back  Change that object and update the database automatically
  • 38. 9th February 2013 38 Replacing SQL  Instead of  SELECT * FROM my_table WHERE my_id = 10  and then dealing with the prepare/execute/fetch code
  • 39. 9th February 2013 39 Replacing SQL  We can write  use My::Object; # warning! not a real orm my $obj = My::Object->retrieve(10)  Or something similar
  • 40. 9th February 2013 40 Perl ORM Options  Plenty of choices on CPAN  Fey::ORM  Rose::DB  Class::DBI  DBIx::Class − The current favourite
  • 42. 9th February 2013 42 DBIx::Class  Standing on the shoulders of giants  Learning from problems in Class::DBI  More flexible  More powerful
  • 43. 9th February 2013 43 DBIx::Class Example  Modeling a CD collection  Three tables  artist (id, name)  cd (id, artist_id, title, year)  track (id, cd_id, title, sequence)
  • 45. 9th February 2013 45 DBIC Classes  Two mandatory types of class  One schema class − CD::Schema  One result class for each table − CD::Schema::Result::Artist − CD::Schema::Result::CD − CD::Schema::Result::Track
  • 46. 9th February 2013 46 Schema Class  Define schema class  CD/Schema.pm  package CD::Schema; use strict; use warnings; use base qw/DBIx::Class::Schema/; __PACKAGE__->load_namespaces(); 1;
  • 47. 9th February 2013 47 Result Classes  Need one result class for every table  Needs to know − The table name − The column names − The primary key − Relationships to other tables
  • 48. 9th February 2013 48 Result Classes  CD/Schema/Result/Artist.pm  package CD::Schema::Result::Artist; use base qw/DBIx::Class::Core/; __PACKAGE__->table('artist'); __PACKAGE__->add_columns( # simple option qw/ id name / ); __PACKAGE__->set_primary_key('id'); __PACKAGE__->has_many( 'cds', 'CD::Schema::Result::CD', 'artist_id' ); 1;
  • 49. 9th February 2013 49 Result Classes  CD/Schema/Result/CD.pm  package CD::Schema::Result::CD; use base qw/DBIx::Class::Core/; __PACKAGE__->table('cd'); __PACKAGE__->add_columns( qw/ id artist_id title year / ); __PACKAGE__->set_primary_key('id'); __PACKAGE__->belongs_to( 'artist', 'CD::Schema::Result::Artist', 'artist_id' ); __PACKAGE__->has_many( 'tracks', 'CD::Schema::Result::Track', 'cd_id' ); 1;
  • 50. 9th February 2013 50 Result Classes  CD/Schema/Result/Track.pm  package CD::Schema::Result::Track; use base qw/DBIx::Class::Core/; __PACKAGE__->table('track'); __PACKAGE__->add_columns( qw/ id cd_id title sequence / ); __PACKAGE__->set_primary_key('id'); __PACKAGE__->belongs_to( 'cd', 'CD::Schema::Result::CD', 'cd_id' ); 1;
  • 51. 9th February 2013 51 Defining Columns  At a minimum you must define column names  But you can give more information  __PACKAGE__->add_columns( id => { data_type => 'integer', is_auto_increment => 1, }, name => { data_type => 'varchar', size => 255, } );
  • 52. 9th February 2013 52 Defining Relationships  We have seen has_many and belongs_to  Both ends of a many-to-one relationship  Most common type of relationship  Artists to CDs  CDs to tracks  Manager to employees  Invoice to invoice lines  Simple foreign key relationship
  • 53. 9th February 2013 53 Other Relationships  has_one − Only one child record − Person has one home address  might_have − Optional has_one relationship  Affects the SQL that is generated
  • 54. 9th February 2013 54 Don't Repeat Yourself  The Pragmatic Programmer says “Don't repeat yourself”  Only one source for every piece of information  We are breaking this rule  We have repeated data
  • 55. 9th February 2013 55 Repeated Information  CREATE TABLE artist ( artistid INTEGER PRIMARY KEY, name TEXT NOT NULL );
  • 56. 9th February 2013 56 Repeated Information  package CD::Schema::Result::Artist; use base qw/DBIx::Class::Core/; __PACKAGE__->table('artist'); __PACKAGE__->add_columns( # simple option qw/ id name / ); __PACKAGE__->set_primary_key('id'); __PACKAGE__->has_many( 'cds', 'CD::Schema::Result::CD', 'artist_id' ); 1;
  • 57. 9th February 2013 57 Don't Repeat Yourself  Information is repeated  Columns and relationships defined in the database schema  Columns and relationships defined in class definitions
  • 58. 9th February 2013 58 Don't Repeat Yourself  Need to define one canonical representation for data definitions  Generate the other one  Let's choose the DDL  Generate the classes from the DDL
  • 59. 9th February 2013 59 Database Metadata  Some people don't put enough metadata in their databases  Just tables and columns  No relationships. No constraints  You may as well make each column VARCHAR(255)
  • 60. 9th February 2013 60 Database Metadata  Describe your data in your database  It's what your database is for  It's what your database does best
  • 61. 9th February 2013 61 DBIC::Schema::Loader  DBIx::Class::Schema::Loader − Separate distribution on CPAN  Creates classes by querying your database metadata  No more repeated data  We are now DRY  Schema definitions in one place
  • 62. 9th February 2013 62 dbicdump  DBIC::Schema::Loader comes with a command line program called dbicdump  $ dbicdump CD::Schema dbi:mysql:database=cd root '' Dumping manual schema for CD::Schema to directory . ... Schema dump completed.  $ find CD CD CD/Schema CD/Schema/Result CD/Schema/Result/Cd.pm CD/Schema/Result/Artist.pm CD/Schema/Result/Track.pm CD/Schema.pm
  • 64. 9th February 2013 Loading DBIC Libraries  Load the main schema class  use CD::Schema;  The load_namespaces call takes care of loading the rest of the classes
  • 65. 9th February 2013 Connecting to DB  The DBIC equivalent of a database handle is called a schema  Get one by calling the connect method  my $sch = CD::Schema->connect( 'dbi:mysql:database=cd', $user, $pass );  Connection parameters passed through to DBI
  • 66. 9th February 2013 Inserting Data  Interact with tables using a resultset object  The schema class has a resultset method that will give you a resultset object  my $art_rs = $sch->resultset('Artist');
  • 67. 9th February 2013 Inserting Artists  Use the create method on a resultset to insert data into a table  my @artists = ('Elbow', 'Arcade Fire'); foreach (@artists) { $art_rs->create({ name => $_ }); }  Pass a hash reference containing data  Handles auto-increment columns
  • 68. 9th February 2013 Inserting Artists  The create method returns a new artist object − Actually a CD::Schema::Result::Artist  my $bowie = $art_rs->create({ name => 'David Bowie' });  Result objects have methods for each column  say $bowie->id;
  • 69. 9th February 2013 Inserting Artists  An alternative is to use the populate() method  my @artists = $art_rs->populate( [ 'name' ], [ 'Arcade Fire' ], [ 'Elbow' ], );  Pass one array reference for each row  First argument is a list of column names
  • 70. 9th February 2013 Insert Related Records  Easy to insert objects related to existing objects  $bowie->add_to_cds({ title => 'The Next Day', year => 2013 });  Foreign key added automatically  add_to_cds method added because of relationships
  • 71. 9th February 2013 Reading Data  Selecting data is also done through a resultset object  We use the search() method  my ($bowie) = $art_rs->search({ name => 'David Bowie' });
  • 72. 9th February 2013 Reading Data  There's also a find() method  Use when you know there's only one matching row  For example, using primary key  my $bowie = $art_rs->find({ id => 3, });  my $bowie = $art_rs->find(3);
  • 73. 9th February 2013 Searching Relationships  Defining relationships allows us to move from object to object easily  my $cd_rs = $sch->resultset('CD'); my ($cd) = $cd_rs->search({ title => 'The Seldom Seen Kid' }); say $cd->artist->name; # Elbow  The artist() method returns the associated artist object
  • 74. 9th February 2013 Searching Relationships  This works the other way too  my ($artist) = $art_rs->search({ name => 'Elbow', }); foreach ($artist->cds) { say $_->title; }  The cds() method returns the associated CD objects
  • 75. 9th February 2013 75 What Search Returns  The search() method returns different things in different contexts  In list context it returns a list of result objects that it has found  In scalar context it returns another resultset − That only contains the matching result objects
  • 76. 9th February 2013 76 What Search Returns  my $artist = $art_rs->search({ name => 'Elbow'; }); − $artist is a resultset object  my ($artist) = $art_rs->search({ name => 'Elbow'; }); − $artist is a result object
  • 77. 9th February 2013 77 Taming Search  To get all of the result objects from a resultset call its all() method  my $artist = $art_rs->search({ name => 'Elbow'; })->all; − $artist is a result object
  • 78. 9th February 2013 78 Taming Search  To get always get a resultset, use search_rs() instead of search()  my ($artist) = $art_rs->search_rs({ name => 'Elbow'; }); − $artist is a resultset object
  • 79. 9th February 2013 Updating Data  Once you have a result object you can change any of its attributes  $bowie->name('Thin White Duke');  Use the update() method to save it to the database  $bowie->update();
  • 80. 9th February 2013 Updating Data  You can also call update() on a resultset  my $davids = $art_rs->search({ name => { like => 'David %' }, }); $davids->update({ name => 'Dave', });
  • 81. 9th February 2013 Deleting Data  Deleting works a lot like updating  Delete a single record  my ($britney) = $art_rs->search({ name => 'Britney Spears' }); $britney->delete;
  • 82. 9th February 2013 Deleting Data  You can also delete a resultset  my $cliffs = $art_rs->search({ name => { like => 'Cliff %' } }); $cliffs->delete;
  • 83. 9th February 2013 Cascading Deletes  What if any of the artists have CDs in the database?  They get deleted too  Referential integrity  Prevent this by changing relationship definition  __PACKAGE__->has_many( 'cds', 'CD::Schema::Result::CD', 'artistid', { cascade_delete => 0 }, );
  • 84. 9th February 2013 Insert Multiple Records  Create can be used to insert many rows  $art_rs->create({ name => 'Arcade Fire', cds => [{ title => 'The Suburbs' }, { title => 'Funeral' }] });
  • 85. 9th February 2013 Find or Insert  Insert an object or return an existing one  my $killers = $art_rs->find_or_create({ name => 'The Killers' });  Note: Need a unique index on one of the search columns
  • 86. 9th February 2013 Update or Create  Update an existing object or create a new one  my $killers = $art_rs->update_or_create({ name => 'The Killers' });  Note: Need a unique index on one of the search columns
  • 87. 9th February 2013 Transactions  Transactions protect the referential integrity of your data  Chunk of work that must all happen  Temporary workspace for DB changes  Commit or rollback at the end
  • 88. 9th February 2013 Transactions & DBIC  Schema object has a txn_do() method  Takes a code reference as a parameter  Adds BEGIN and COMMIT (or ROLLBACK) around code  Transactions can include Perl code
  • 89. 9th February 2013 Transactions & DBIC  $schema->txn_do( sub { my $obj = $rs->create(%some_obj); $obj->add_to_children(%some_child); });
  • 91. 9th February 2013 Advanced Searches  search() can be used for more complex searchs  See SQL::Abstract documentation for full details
  • 92. 9th February 2013 AND  Use a hash reference to combine conditions using AND  $person_rs->search({ forename => 'Dave', email => 'dave@perlschool.co.uk' });  WHERE forename = 'Dave' AND email = 'dave@perlschool.co.uk'
  • 93. 9th February 2013 OR  Use an array reference to combine conditions using OR  $person_rs->search([{ forename => 'Dave' }, { email => 'dave@perlschool.co.uk' }]);  WHERE forename = 'Dave' OR email = 'dave@perlschool.co.uk'
  • 94. 9th February 2013 Combinations  Combine hash references and array references for more flexibility  $person_rs->search([{ forename => 'Dave', username => 'dave' }, { email = 'dave@perlschool.co.uk' }]);
  • 95. 9th February 2013 Many Values for Column  Use an array reference to test many values for a column  $person_rs->search({ forename => [ 'Dave', 'David' ] });  WHERE forename = 'Dave' OR forename = 'David'
  • 96. 9th February 2013 Using SQL  SQL::Abstract supports some SQL options  $person_rs->search({ forename => { like => 'Dav%' } });  WHERE forename LIKE 'Dav%'
  • 97. 9th February 2013 Using SQL  More SQL-like options  $person_rs->search({ forename => { '-in' => [ 'Dave', 'David' ] } });  WHERE forename IN ('Dave', 'David')
  • 98. 9th February 2013 Using SQL  More SQL-like options  $person_rs->search({ birth_year => { '-between' => [ 1970, 1980 ] } });  WHERE birth_year BETWEEN 1970 AND 1980
  • 99. 9th February 2013 Extra Search Attributes  All of our examples have used one parameter to search  $rs->search(%where_clause)  Search takes an optional second parameter  Defines search attributes  $rs->search(%where_clause, %attrs)
  • 100. 9th February 2013 Select Specific Columns  Default search selects all columns in a table − Actually all attributes in the class  Use the columns attribute to change this  $person_rs->search({ forename => 'Dave' }, { columns => [ 'me.forename', 'me.surname' ] });  Note table aliases
  • 101. 9th February 2013 Add Columns  You can invent columns and add them to the returned object  $person_rs->search({ forename => 'Dave' }, { +columns => { namelen => { length => 'me.forename' } } });  Use get_column() to access this data  $person->get_column('namelen')
  • 102. 9th February 2013 Ordering Data  Use search attributes to order the data  $person_rs->search({ forename => 'Dave' }, { order => { '-asc' => [ 'me.surname' ] } });
  • 103. 9th February 2013 Paging  Select a subset of the data  $person_rs->search({ forename => 'Dave', }, { rows => 10, page => 2 });  You probably want to sort that query
  • 104. 9th February 2013 Joining Tables  Use the join attribute to join to other tables  $art_rs->search({}, { columns => [ 'me.name', 'cds.title' ], join => [ 'cds' ] });  Join artist table to CD table  Return artist name and CD title
  • 105. 9th February 2013 Aggregate Functions  Use SQL aggregate functions like COUNT, SUM and AVERAGE  $person_rs->search({}, { columns => [ 'me.forename', name_count => { count => 'me.forename' } ], group_by => [ 'me.forename' ] });  Use get_columns() to get the count
  • 106. 9th February 2013 Join and Aggregate  Combine joins and aggregates  $art_rs->search({}, { columns => [ 'me.name', cd_count => { count => 'cds.id' } ], group_by => [ 'me.forename' ], join => [ 'cds' ] });
  • 107. 9th February 2013 Chaining Resultsets  We said that search() can return a resultset  We can call search() again on that resultset to further specify the search  And so on...
  • 108. 9th February 2013 Chaining Resultsets  my $daves = $person_rs->search({ forename => 'Dave' }); my $women => $daves_rs->search({ sex => 'F' }); foreach ($women->all) { say $_->forename, ' ', $_->surname; }
  • 109. 9th February 2013 Executing Resultsets  A resultset is the definition of a query  The query isn't run until you execute the resultset  By calling all(), first(), next(), etc − $person_rs->all  By calling search() in list context − @daves = $person_rs->search({ forename => 'Dave', });
  • 110. More on Result Classes
  • 111. 9th February 2013 Result Classes  Result classes are usually generated by DBIx::Class::Schema::Loader  Define columns  Define relationships  But we can add our own code to these classes
  • 112. 9th February 2013 112 Derived Columns  Sometimes it's handy to have a “column” that is derived from other columns  Just add a method  sub name { my $self = shift; return $self->forename, ' ', $self->surname; }
  • 113. 9th February 2013 113 Actions  Add methods defining actions that your class needs to carry out  sub marry { my $self = shift; my $spouse = shift; $self->spouse($spouse->id); $spouse->spouse($self->id); }
  • 114. 9th February 2013 114 Column Inflation  Inflate a column into a more useful class when reading from database  Deflate object into string before saving to database  e.g. Convert datetime column to DateTime object
  • 115. 9th February 2013 115 DateTime Inflation  This is a standard feature of DBIC  DBIx::Class::InflateColumn::DateTime  Load as a component − __PACKAGE__->load_component( 'DBIx::Class::InflateColumn::DateTime' );  Define column as datetime − __PACKAGE__->add_columns( birth => { datatype => 'datetime' } );
  • 116. 9th February 2013 116 DateTime Inflation  my $person = $person_rs->first; my $birth = $person->birth; say ref $birth; # DateTime say $birth->day_name;  $person_rs->create({ name => 'Some Person', birth => DateTime->now });
  • 117. 9th February 2013 117 DBIC::Schema::Loader  Use the -o command line option to include components in generated classes  dbicdump -o components='[“InflateColumn::DateTime”]' ...  Adds the load_components() call to the classes
  • 118. 9th February 2013 118 Manual Inflation  You can define your own inflation/deflation code  Use the inflate_column() method  __PACKAGE__->inflate_column( 'column_name' => { inflate_column => sub { ... }, deflate_column => sub { ... }, } );
  • 119. 9th February 2013 119 Unicode Inflation  Databases store strings as a series of bytes  Well-behaved Unicode-aware code converts bytes to characters as the string enters the program − And vice versa  Many DBDs have a flag to do this automatically  Some don't
  • 120. 9th February 2013 120 Unicode Inflation  use Encode; __PACKAGE__->inflate_column( 'some_text_column' => { inflate_column => sub { return decode('utf8', $_[0]); }, deflate_column => sub { return encode('utf8', $_[0]); }, } );
  • 121. 9th February 2013 121 Relationships  DBIx::Class::Schema::Loader generates many kinds of relationships from metadata  It doesn't recognise many-to-many relationships − Linking tables  We can add them manually in the result class
  • 122. 9th February 2013 122 Many to Many  An actor appears in many films  A film features many actors  How do you model that relationship?  Add a linking table − Appearance  Two foreign keys
  • 124. 9th February 2013 124 Many to Many  DBIx::Class::Schema::Loader finds the standard relationships − Actor has many Appearances − Appearances belong to Actor − Film has many Appearances − Appearances belong to Film  We can add a many to many relationship − In both directions
  • 125. 9th February 2013 Many to Many  Film::Schema::Result::Actor->many_to_many( 'films', # new relationship name 'appearances', # linking relationship 'film' # FK relationship in link table ); Film::Schema::Result::Film->many_to_many( 'actors', # new relationship name 'appearances', # linking relationship 'actor', # FK relationship in link table );
  • 126. 9th February 2013 Without Many to Many  my $depp = $actor_rs->search({ name => 'Johnny Depp' }); foreach ($depp->appearances) { say $_->film->title; }
  • 127. 9th February 2013 With Many to Many  my $depp = $actor_rs->search({ name => 'Johnny Depp' }); foreach ($depp->films) { say $_->title; }
  • 128. 9th February 2013 Editing Result Classes  Editing result classes is useful  But result classes are usually generated − DBIx::Class::Schema::Loader  How do we regenerate classes?  Without overwriting our additions
  • 129. 9th February 2013 MD5 Hash  A generated result class contains an MD5 hash  # Created by DBIx::Class::Schema::Loader v0.05003 @ 2010-04-04 13:53:54 # DO NOT MODIFY THIS OR ANYTHING ABOVE! md5sum:IvAzC9/WLrHifAi0APmuRw  Add anything below this line  Code below this line is preserved on regeneration
  • 130. 9th February 2013 Resultset Classes  We've looked a lot at editing result classes  You can also edit resultset classes  Often to add new search methods  But resultset classes don't exist as files  Need to create them first
  • 131. 9th February 2013 Resultset Class  package App::Schema::Resultset::Person use strict; use warnings; use base 'DBIx::Class::Resultset'; 1;
  • 132. 9th February 2013 Default Search Values  sub search_men { my $self = shift; return $self->search({ sex => 'M' }); }
  • 133. 9th February 2013 Default Search Values  sub search_men { my $self = shift; my ($cols, $opts) = @_; $cols ||= {}; $opts ||= {}; $cols->{sex} = 'M'; return $self->search( $cols, $opts ); }
  • 134. 9th February 2013 Default Search Options  sub search_sorted { my $self = shift; return $self->search({}, { order_by => 'name ASC' }); }  Similar changes for full version
  • 136. 9th February 2013 136 Extending DBIC  DBIC is powerful and flexible  Most of the time it can be made to do what you want  Sometimes you need to change its default behaviour  Override default methods
  • 137. 9th February 2013 137 Overriding Methods  Overriding methods is a standard OO technique  Method in a subclass replaces one in a superclass  Define subclass method with same name  Subclass method has new behaviour
  • 138. 9th February 2013 138 Overriding Methods  Often the subclass behaviour needs to happen in addition to the superclass behaviour  Subclass method needs to call the superclass method  Ugly syntax  $self->SUPER::method()
  • 139. 9th February 2013 139 Overriding Methods  sub do_something { my $self = shift; ... $self->SUPER::do_something(@_); ... }
  • 140. 9th February 2013 140 Class::C3 / mro  DBIC uses a non-standard method resolution technique  mro − Method resolution order  Specifically its Class::C3 implementation  “better consistency in multiple inheritance situations”
  • 141. 9th February 2013 141 Class::C3 / mro  All you really need to know  When overloading DBIC methods, use $self->next::method instead of SUPER  sub do_something { my $self = shift; ... $self->next::method(@_); ... }
  • 142. 9th February 2013 142 Overriding new()  Result classes don't include a new method  That's defined in the DBIx::Class superclass  We can override it  sub new { my $class = shift; # do stuff return $self->next::method(@_); }
  • 143. 9th February 2013 143 Overriding new()  Defaults for missing attributes  sub new { my $class = shift; my $obj = shift; # Set birthday if it's missing $obj->{birth} ||= DateTime->now; # Superclass method does real work return $self->next::method($obj); }
  • 144. 9th February 2013 144 Overriding update()  Add audit information  sub update { my $self = shift; # Set audit columns $self->upd_time(DateTime->now); $self->upd_by($Curr_User); # Superclass method does real work $self->next::method(); say $self->name, ' updated'; }
  • 145. 9th February 2013 145 Overriding delete()  Don't really delete rows  sub delete { my $self = shift; # Set deleted flag $self->deleted(1); # Don't call superclass method! $self->update; }
  • 146. 9th February 2013 146 DBIC and Moose  Moose is the future of OO Perl  Moose makes OO Perl easier, more powerful and more flexible  Moose supports use alongside non-Moose classes − MooseX::NonMoose  We can use DBIC with Moose
  • 147. 9th February 2013 147 Write Your Own Classes  package CD::Schema::Result::Artist; use Moose; use MooseX::NonMoose; extends 'DBIx::Class:Core'; __PACKAGE__->table('artist'); __PACKAGE__->add_columns(...); __PACKAGE__->set_primary_key(...); # define relationships ... __PACKAGE__->meta->make_immutable;
  • 148. 9th February 2013 148 Write Your Own Classes  package CD::Schema::Result::Artist; use Moose; use MooseX::NonMoose; extends 'DBIx::Class:Core'; __PACKAGE__->table('artist'); __PACKAGE__->add_columns(...); __PACKAGE__->set_primary_key(...); # define relationships ... __PACKAGE__->meta->make_immutable;
  • 149. 9th February 2013 149 Using Moose Class  As far as the user (i.e. the application programmer) is concerned there is no difference  The same code will work  my $artist_rs = $schema->resultset('Artist');  my $artist = $art_rs->create(%artist);  $artist->update;  $artist_rs->search();
  • 150. 9th February 2013 150 Using Moose Class  For the programmer writing the class, life gets better  We now have all of the power of Moose  Particularly for overriding methods  Method modifiers
  • 151. 9th February 2013 151 Method Modifiers  More flexible and powerful syntax for overriding methods  More control over interaction between subclass method and superclass method  Easier syntax − No $self->SUPER::something() − No $self->next::method()
  • 152. 9th February 2013 152 Overriding new()  Run subclass method before superclass method  before new => sub { my $class = shift; my $obj = shift; # Set birthday if it's missing $obj->{birth} ||= DateTime->now; # Superclass method run # automatically }
  • 153. 9th February 2013 153 Overriding update()  Run subclass method around superclass method  around update => sub { my $orig = shift; my $self = shift; # Set audit columns $self->upd_time(DateTime->now); $self->upd_by($Curr_User); # Superclass method does real work $self->$orig(@_); say $self->name, ' updated'; }
  • 154. 9th February 2013 154 Overriding delete()  Run subclass method in place of superclass method  override delete => sub { my $self = shift; # Set deleted flag $self->deleted(1); # Don't call superclass method! $self->update; }
  • 155. 9th February 2013 155 Adding Roles  Moose roles are pre-packaged features that can be added into your class  Like mixins or interfaces in other OO languages  Added with the keyword “with”
  • 156. 9th February 2013 156 Role Example  package App::Schema::Result::SomeTable; use Moose; use MooseX::NonMoose; extends 'DBIx::Class::Core'; with 'Some::Clever::Role';
  • 157. 9th February 2013 157 DBIC::Schema::Loader  DBIx::Class::Schema::Loader has built-in support for Moose  use_moose option  With dbicdump  $ dbicdump -o use_moose=1 CD::Schema dbi:mysql:database=cd root ''  Creates classes with the Moose lines included
  • 159. 9th February 2013 Changing Schemas  Database schemas change over time  Tables added  Columns added  Column definitions change  DBIC has tools to manage that
  • 160. 9th February 2013 Don't Repeat Yourself  We have two definitions of our database schema  DDL − CREATE TABLE, etc  DBIC − Perl code  Choose one as canonical source
  • 161. 9th February 2013 DDL vs DBIC  We can create DBIC code from DDL − DBIx::Class::Schema::Loader  We can create DDL from DBIC − $schema->deploy()
  • 162. 9th February 2013 Deploy  Schema objects have a deploy() method  Generates DDL − Using SQL::Translator − Applies it to connected database  Can also see the DDL − deployment_statements() − create_ddl_dir()
  • 163. 9th February 2013 Schema Versions  Versions change over time  Need to cope with that  Add a version to our schema class  Set $VERSION
  • 164. 9th February 2013 Schema Versions  package CD::Schema; use warnings; use strict; use base 'DBIx::Class::Schema'; our $VERSION = '0.01'; __PACKAGE__->load_namespaces(); 1;
  • 165. 9th February 2013 Schema Versions  package CD::Schema; use warnings; use strict; use base 'DBIx::Class::Schema'; our $VERSION = '0.01'; __PACKAGE__->load_namespaces(); 1;
  • 166. 9th February 2013 create_ddl_dir  The create_ddl_dir() method is clever  Given a previous version of a schema  It can create ALTER TABLE statements  $schema->create_ddl_dir( [ 'MySQL' ], $curr_ver, $directory, $preversion );  This will be very useful
  • 167. 9th February 2013 Deploying Versions  DBIC includes a module called DBIx::Class::Schema::Versioned  Upgrades schemas
  • 168. 9th February 2013 DBIC::Sch::Versioned  More changes to your schema class  package MyApp::Schema; use base qw/DBIx::Class::Schema/; our $VERSION = 0.001; __PACKAGE__->load_namespaces; __PACKAGE__->load_components( qw/Schema::Versioned/ ); __PACKAGE__->upgrade_directory( '/path/to/upgrades/' );
  • 169. 9th February 2013 DBIC::Sch::Versioned  More changes to your schema class  package MyApp::Schema; use base qw/DBIx::Class::Schema/; our $VERSION = 0.001; __PACKAGE__->load_namespaces; __PACKAGE__->load_components( qw/Schema::Versioned/ ); __PACKAGE__->upgrade_directory( '/path/to/upgrades/' );
  • 170. 9th February 2013 Create Upgrade DDL  use Getopt::Long; use CD::Schema; my $preversion, $help; GetOptions( 'p|preversion:s' => $preversion, ) or die; my $schema = MyApp::Schema->connect(...); # continued...
  • 171. 9th February 2013 Create Upgrade DDL  my $sql_dir = './sql';  my $version = $schema->schema_version();  $schema->create_ddl_dir( 'MySQL', $version, $sql_dir, $preversion );  Creates all the DDL you need − Includes versioning tables
  • 172. 9th February 2013 Upgrade DB  use CD::Schema; my $schema = CD::Schema->connect(...); if ($schema->get_db_version()) { # Runs all the upgrade SQL $schema->upgrade(); } else { # Schema is unversioned # Installs empty tables $schema->deploy(); }
  • 173. 9th February 2013 Better Tool  DBIC::Schema::Versioned is part of the standard DBIC package  DBIC::DeploymentHandler is a separate CPAN package  More powerful  More flexible
  • 174. 9th February 2013 DBIC::DeploymentHndlr  Advantages − Upgrades and downgrades − Multiple SQL files in one upgrade − Use Perl scripts for upgrade  Disadvantages − Dependency hell
  • 176. 9th February 2013 Replication  Some databases allow multiple copies of the same data  Server software keeps replicants in step  This can aid performance  Different clients can talk to different servers  Data on some replicants can lag
  • 177. 9th February 2013 Types of Replication  Master-Slave − One writeable copy of the database − Many readable replicants − e.g. MySQL
  • 178. 9th February 2013 Types of Replication  Multiple Master − Many writeable copies − Potential for deadlocks − e.g. Sybase
  • 179. 9th February 2013 DBIC & Replication  DBIC has beta support for master/slave replication  Directs all writes to master connection  Directs all reads to slave connection
  • 180. 9th February 2013 DBIC & Replication  Set the storage_type attribute on our schema object  my $schema = CD::Schema->connect(...); $schema->storage_type([ '::DBI::Replicated', { balancer => 'Random' }, ]);
  • 181. 9th February 2013 Add Slaves  Add slave connections  $schema->storage->connect_replicants( [$dsn1, $user, $pass, %opts], [$dsn2, $user, $pass, %opts], [$dsn3, $user, $pass, %opts], );
  • 182. 9th February 2013 Use Schema  Use schema as usual  Reads are delegated to a random slave  Writes are delegated to the master  You can force a read to the master  $rs->search({ ... }, { force_pool => 'master' }); − Avoid race conditions
  • 184. 9th February 2013 Documentation  Lots of good DBIC documentation − perldoc DBIx::Class − perldoc DBIx::Class::Manual  DBIx::Class::Manual::SQLHackers − Separate documentation distribution
  • 185. 9th February 2013 Support  Web site − http://www.dbix-class.org/  Mailing list − See support page on web site  IRC channel − #dbix-class on irc.perl.org
  • 186. 9th February 2013 Books  Good coverage in The Definitive Guide to Catalyst − Not completely up to date  DBIC book being written − Schedule unknown
  • 187. That's All Folks • Any Questions?