Mojo::Pg(3)

NAME
Mojo::Pg - Mojolicious ♥ PostgreSQL

SYNOPSIS
  use Mojo::Pg;

  # Create a table
  my $pg = Mojo::Pg->new('postgresql://postgres@/test');
  $pg->db->query('create table names (id serial primary key, name text)');

  # Insert a few rows
  my $db = $pg->db;
  $db->query('insert into names (name) values (?)', 'Sara');
  $db->query('insert into names (name) values (?)', 'Stefan');

  # Insert more rows in a transaction
  eval {
    my $tx = $db->begin;
    $db->query('insert into names (name) values (?)', 'Baerbel');
    $db->query('insert into names (name) values (?)', 'Wolfgang');
    $tx->commit;
  };
  say $@ if $@;

  # Insert another row and return the generated id
  say $db->query('insert into names (name) values (?) returning id', 'Daniel')
    ->hash->{id};

  # JSON roundtrip
  say $db->query('select ?::json as foo', {json => {bar => 'baz'}})
    ->expand->hash->{foo}{bar};

  # Select one row at a time
  my $results = $db->query('select * from names');
  while (my $next = $results->hash) {
    say $next->{name};
  }

  # Select all rows blocking
  $db->query('select * from names')
    ->hashes->map(sub { $_->{name} })->join("\n")->say;

  # Select all rows non-blocking
  Mojo::IOLoop->delay(
    sub {
      my $delay = shift;
      $db->query('select * from names' => $delay->begin);
    },
    sub {
      my ($delay, $err, $results) = @_;
      $results->hashes->map(sub { $_->{name} })->join("\n")->say;
    }
  )->wait;

  # Send and receive notifications non-blocking
  $pg->pubsub->listen(foo => sub {
    my ($pubsub, $payload) = @_;
    say "foo: $payload";
    $pubsub->notify(bar => $payload);
  });
  $pg->pubsub->listen(bar => sub {
    my ($pubsub, $payload) = @_;
    say "bar: $payload";
  });
  $pg->pubsub->notify(foo => 'PostgreSQL rocks!');
  Mojo::IOLoop->start unless Mojo::IOLoop->is_running;

DESCRIPTION
Mojo::Pg is a tiny wrapper around DBD::Pg that makes PostgreSQL <http://www.postgresql.org> a lot of fun to use with the Mojolicious <http://mojolicious.org> real-time web framework.

Database and statement handles are cached automatically, so they can be reused transparently to increase performance. And you can handle connection timeouts gracefully by holding on to them only for short amounts of time.

  use Mojolicious::Lite;
  use Mojo::Pg;

  helper pg =>
    sub { state $pg = Mojo::Pg->new('postgresql://sri:s3cret@localhost/db') };

  get '/' => sub {
    my $c  = shift;
    my $db = $c->pg->db;
    $c->render(json => $db->query('select now() as time')->hash);
  };

  app->start;

While all I/O operations are performed blocking, you can wait for long running queries asynchronously, allowing the Mojo::IOLoop event loop to perform other tasks in the meantime. Since database connections usually have a very low latency, this often results in very good performance.

Every database connection can only handle one active query at a time, this includes asynchronous ones. To perform multiple queries concurrently, you have to use multiple connections.

  # Performed concurrently (5 seconds)
  $pg->db->query('select pg_sleep(5)' => sub {...});
  $pg->db->query('select pg_sleep(5)' => sub {...});

All cached database handles will be reset automatically if a new process has been forked, this allows multiple processes to share the same Mojo::Pg object safely.

EVENTS
Mojo::Pg inherits all events from Mojo::EventEmitter and can emit the following new ones.

  connection
  $pg->on(connection => sub {
    my ($pg, $dbh) = @_;
    ...
  });

Emitted when a new database connection has been established.

  $pg->on(connection => sub {
    my ($pg, $dbh) = @_;
    $dbh->do('set search_path to my_schema');
  });

ATTRIBUTES
Mojo::Pg implements the following attributes.

  dsn
  my $dsn = $pg->dsn;
  $pg     = $pg->dsn('dbi:Pg:dbname=foo');

Data source name, defaults to "dbi:Pg:".

  max_connections
  my $max = $pg->max_connections;
  $pg     = $pg->max_connections(3);

Maximum number of idle database handles to cache for future use, defaults to 5.

  migrations
  my $migrations = $pg->migrations;
  $pg            = $pg->migrations(Mojo::Pg::Migrations->new);

Mojo::Pg::Migrations object you can use to change your database schema more easily.

  # Load migrations from file and migrate to latest version
  $pg->migrations->from_file('/home/sri/migrations.sql')->migrate;

  options
  my $options = $pg->options;
  $pg         = $pg->options({AutoCommit => 1, RaiseError => 1});

Options for database handles, defaults to activating "AutoCommit", "AutoInactiveDestroy" as well as "RaiseError" and deactivating "PrintError". Note that "AutoCommit" and "RaiseError" are considered mandatory, so deactivating them would be very dangerous.

  password
  my $password = $pg->password;
  $pg          = $pg->password('s3cret');

Database password, defaults to an empty string.

  pubsub
  my $pubsub = $pg->pubsub;
  $pg        = $pg->pubsub(Mojo::Pg::PubSub->new);

Mojo::Pg::PubSub object you can use to send and receive notifications very efficiently, by sharing a single database connection with many consumers.

  # Subscribe to a channel
  $pg->pubsub->listen(news => sub {
    my ($pubsub, $payload) = @_;
    say "Received: $payload";
  });

  # Notify a channel
  $pg->pubsub->notify(news => 'PostgreSQL rocks!');

  search_path
  my $path = $pg->search_path;
  $pg      = $pg->search_path(['$user', 'foo', 'public']);

Schema search path assigned to all new connections.

  # Isolate tests and avoid race conditions when running them in parallel
  $pg->search_path(['test_one']);
  $pg->migrations->migrate(0)->migrate;

  username
  my $username = $pg->username;
  $pg          = $pg->username('sri');

Database username, defaults to an empty string.

METHODS
Mojo::Pg inherits all methods from Mojo::EventEmitter and implements the following new ones.

  db
  my $db = $pg->db;

Get Mojo::Pg::Database object for a cached or newly established database connection. The DBD::Pg database handle will be automatically cached again when that object is destroyed, so you can handle problems like connection timeouts gracefully by holding on to it only for short amounts of time.

  # Add up all the money
  say $pg->db->query('select * from accounts')
    ->hashes->reduce(sub { $a->{money} + $b->{money} });

  from_string
  $pg = $pg->from_string('postgresql://postgres@/test');

Parse configuration from connection string.

  # Just a database
  $pg->from_string('postgresql:///db1');

  # Just a service
  $pg->from_string('postgresql://?service=foo');

  # Username and database
  $pg->from_string('postgresql://sri@/db2');

  # Username, password, host and database
  $pg->from_string('postgresql://sri:s3cret@localhost/db3');

  # Username, domain socket and database
  $pg->from_string('postgresql://sri@%2ftmp%2fpg.sock/db4');

  # Username, database and additional options
  $pg->from_string('postgresql://sri@/db5?PrintError=1&pg_server_prepare=0');

  # Service and additional options
  $pg->from_string('postgresql://?service=foo&PrintError=1&RaiseError=0');

  new
  my $pg = Mojo::Pg->new;
  my $pg = Mojo::Pg->new('postgresql://postgres@/test');

Construct a new Mojo::Pg object and parse connection string with "from_string" if necessary.

  # Customize configuration further
  my $pg = Mojo::Pg->new->dsn('dbi:Pg:service=foo');

REFERENCE
This is the class hierarchy of the Mojo::Pg distribution.

•   Mojo::Pg

•   Mojo::Pg::Database

•   Mojo::Pg::Migrations

•   Mojo::Pg::PubSub

•   Mojo::Pg::Results

•   Mojo::Pg::Transaction

AUTHOR
Sebastian Riedel, "sri@cpan.org".

CREDITS
In alphabetical order:

    Dan Book

    Hernan Lopes

COPYRIGHT AND LICENSE
Copyright (C) 2014-2016, Sebastian Riedel.

This program is free software, you can redistribute it and/or modify it under the terms of the Artistic License version 2.0.

SEE ALSO
<https://github.com/kraih/mojo-pg>, Mojolicious::Guides, <http://mojolicious.org>.