NAME
    Mojo::mysql - Mojolicious and Async MySQL

SYNOPSIS
      use Mojo::mysql;

      # Create a table
      my $mysql = Mojo::mysql->strict_mode('mysql://username@/test');
      $mysql->db->query(
        'create table names (id integer auto_increment primary key, name text)');

      # Insert a few rows
      my $db = $mysql->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 (?)', 'Daniel')
        ->last_insert_id;

      # Use SQL::Abstract to generate queries for you
      $db->insert('names', {name => 'Isabel'});
      say $db->select('names', undef, {name => 'Isabel'})->hash->{id};
      $db->update('names', {name => 'Bel'}, {name => 'Isabel'});
      $db->delete('names', {name => 'Bel'});

      # 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;

      # Concurrent non-blocking queries (synchronized with promises)
      my $now   = $db->query_p('select now() as now');
      my $names = $db->query_p('select * from names');
      Mojo::Promise->all($now, $names)->then(sub {
        my ($now, $names) = @_;
        say $now->[0]->hash->{now};
        say $_->{name} for $names->[0]->hashes->each;
      })->catch(sub {
        my $err = shift;
        warn "Something went wrong: $err";
      })->wait;

      # Send and receive notifications non-blocking
      $mysql->pubsub->listen(foo => sub {
        my ($pubsub, $payload) = @_;
        say "foo: $payload";
        $pubsub->notify(bar => $payload);
      });
      $mysql->pubsub->listen(bar => sub {
        my ($pubsub, $payload) = @_;
        say "bar: $payload";
      });
      $mysql->pubsub->notify(foo => 'MySQL rocks!');

      Mojo::IOLoop->start unless Mojo::IOLoop->is_running;

DESCRIPTION
    Mojo::mysql is a tiny wrapper around DBD::mysql that makes MySQL
    <http://www.mysql.org> a lot of fun to use with the Mojolicious
    <http://mojolicio.us> real-time web framework.

    Database and 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::mysql;

      helper mysql =>
        sub { state $mysql = Mojo::mysql->strict_mode('mysql://sri:s3cret@localhost/db') };

      get '/' => sub {
        my $c  = shift;
        my $db = $c->mysql->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. 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 = $mysql->db;
      $db->query('select sleep(5)' => sub {...});
      $db->query('select sleep(5)' => sub {...});

      # Performed concurrently (5 seconds)
      $mysql->db->query('select sleep(5)' => sub {...});
      $mysql->db->query('select 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::mysql object safely.

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

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

    Emitted when a new database connection has been established.

ATTRIBUTES
    Mojo::mysql implements the following attributes.

  abstract
      $abstract = $mysql->abstract;
      $mysql    = $mysql->abstract(SQL::Abstract->new);

    SQL::Abstract object used to generate CRUD queries for
    Mojo::mysql::Database.

      # Generate statements and bind values
      my ($stmt, @bind) = $mysql->abstract->select('names');

  auto_migrate
      my $bool = $mysql->auto_migrate;
      $mysql   = $mysql->auto_migrate($bool);

    Automatically migrate to the latest database schema with "migrations",
    as soon as the first database connection has been established.

    Defaults to false.

  database_class
      $class = $mysql->database_class;
      $mysql = $mysql->database_class("MyApp::Database");

    Class to be used by "db", defaults to Mojo::mysql::Database. Note that
    this class needs to have already been loaded before "db" is called.

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

    Data Source Name, defaults to "dbi:mysql:dbname=test".

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

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

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

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

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

    MySQL does not support nested transactions and DDL transactions. DDL
    statements cause implicit "COMMIT". "ROLLBACK" will be called if any
    step of migration script fails, but only DML statements after the last
    implicit or explicit "COMMIT" can be reverted. Not all MySQL storage
    engines (like "MYISAM") support transactions.

    This means database will most likely be left in unknown state if
    migration script fails. Use this feature with caution and remember to
    always backup your database.

  options
      my $options = $mysql->options;
      $mysql      = $mysql->options({mysql_use_result => 1});

    Options for database handles, defaults to activating
    "mysql_enable_utf8", "AutoCommit", "AutoInactiveDestroy" as well as
    "RaiseError" and deactivating "PrintError". Note that "AutoCommit" and
    "RaiseError" are considered mandatory, so deactivating them would be
    very dangerous.

    "mysql_auto_reconnect" is never enabled, Mojo::mysql takes care of dead
    connections.

    "AutoCommit" cannot not be disabled, use $db->begin to manage
    transactions.

    "RaiseError" is enabled for blocking and disabled in event loop for
    non-blocking queries.

    Note about "mysql_enable_utf8":

      The mysql_enable_utf8 sets the utf8 charset which only supports up to 3-byte
      UTF-8 encodings. mysql_enable_utf8mb4 (as of DBD::mysql 4.032) properly
      supports encoding unicode characters to up to 4 bytes, such as 𠜎. It means the
      connection charset will be utf8mb4 (supported back to at least mysql 5.5) and
      these unicode characters will be supported, but no other changes.

    See also <https://github.com/jhthorsen/mojo-mysql/pull/32>

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

    Database password, defaults to an empty string.

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

    Mojo::mysql::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
      $mysql->pubsub->listen(news => sub {
        my ($pubsub, $payload) = @_;
        say "Received: $payload";
      });

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

    Note that Mojo::mysql::PubSub should be considered an experiment!

  username
      my $username = $mysql->username;
      $mysql       = $mysql->username('batman');

    Database username, defaults to an empty string.

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

  db
      my $db = $mysql->db;

    Get Mojo::mysql::Database object for a cached or newly created database
    handle. The 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
      $mysql = $mysql->from_string('mysql://user@/test');

    Parse configuration from connection string.

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

      # Username and database
      $mysql->from_string('mysql://batman@/db2');

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

      # Username, domain socket and database
      $mysql->from_string('mysql://batman@%2ftmp%2fmysql.sock/db4');

      # Username, database and additional options
      $mysql->from_string('mysql://batman@/db5?PrintError=1&RaiseError=0');

  new
      my $mysql = Mojo::mysql->new;
      my $mysql = Mojo::mysql->new(%attrs);
      my $mysql = Mojo::mysql->new(\%attrs);
      my $mysql = Mojo::mysql->new('mysql://user@/test');

    Construct a new Mojo::mysql object either from "ATTRIBUTES" and or parse
    connection string with "from_string" if necessary.

  strict_mode
      my $mysql = Mojo::mysql->strict_mode('mysql://user@/test');
      my $mysql = $mysql->strict_mode($boolean);

    This method can act as both a constructor and a method. When called as a
    constructor, it will be the same as:

      my $mysql = Mojo::mysql->new('mysql://user@/test')->strict_mode(1);

    Enabling strict mode will execute the following statement when a new
    connection is created:

      SET SQL_MODE = CONCAT('ANSI,TRADITIONAL,ONLY_FULL_GROUP_BY,', @@sql_mode)
      SET SQL_AUTO_IS_NULL = 0

    The idea is to set up a connection that makes it harder for MySQL to
    allow "invalid" data to be inserted.

    This method will not be removed, but the internal commands is subject to
    change.

DEBUGGING
    You can set the "DBI_TRACE" environment variable to get some advanced
    diagnostics information printed to "STDERR" by DBI.

      DBI_TRACE=1

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

    * Mojo::mysql

    * Mojo::mysql::Database

    * Mojo::mysql::Migrations

    * Mojo::mysql::PubSub

    * Mojo::mysql::Results

    * Mojo::mysql::Transaction

AUTHOR
    Curt Hochwender - "hochwender@centurytel.net".

    Dan Book - "dbook@cpan.org"

    Jan Henning Thorsen - "jhthorsen@cpan.org".

    Mike Magowan

    This code is mostly a rip-off from Sebastian Riedel's Mojo::Pg.

COPYRIGHT AND LICENSE
    Copyright (C) 2014-2015, Jan Henning Thorsen.

    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/jhthorsen/mojo-mysql>,

    Mojo::Pg Async Connector for PostgreSQL using DBD::Pg,
    <https://github.com/kraih/mojo-pg>,

    Mojo::MySQL5 Pure-Perl non-blocking I/O MySQL Connector,
    <https://github.com/harry-bix/mojo-mysql5>,

    Mojolicious::Guides, <http://mojolicio.us>.