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35 non-PAUSE users.

Sebastian Riedel

NAME

Mojo::Pg - Mojolicious ♥ PostgreSQL

SYNOPSIS

  use Mojo::Pg;

  # Create a table
  my $pg = Mojo::Pg->new('postgresql://postgres@/test');
  $pg->db->do('create table if not exists names (name varchar(255))');

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

  # 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->pluck('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->pluck('name')->join("\n")->say;
    }
  )->wait;

DESCRIPTION

Mojo::Pg is a tiny wrapper around DBD::Pg that makes PostgreSQL a lot of fun to use with the Mojolicious real-time web framework.

Database and statement handles are cached automatically, so they can be reused transparently to increase performance. 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. So if you start more than one, they will be put on a waiting list and performed sequentially. To perform multiple queries concurrently, you have to use multiple connections.

  # Performed sequentially (10 seconds)
  my $db = $pg->db;
  $db->query('select pg_sleep(5)' => sub {...});
  $db->query('select pg_sleep(5)' => sub {...});

  # 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.

Note that this whole distribution is EXPERIMENTAL and will change without warning!

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.

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('/Users/sri/migrations.sql')->migrate;

options

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

Options for database handles, defaults to activating AutoCommit as well as RaiseError and deactivating PrintError.

password

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

Database password, defaults to an empty string.

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 connection timeouts gracefully by holding on to it only for short amounts of time.

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&RaiseError=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');

AUTHOR

Sebastian Riedel, sri@cpan.org.

COPYRIGHT AND LICENSE

Copyright (C) 2014, 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://mojolicio.us.