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Dan Book

NAME

Mojo::SQLite - A tiny Mojolicious wrapper for SQLite

SYNOPSIS

  use Mojo::SQLite;

  # Select the library version
  my $sql = Mojo::SQLite->new('sqlite:test.db');
  say $sql->db->query('select sqlite_version() as version')->hash->{version};

  # Use migrations to create a table
  $sql->migrations->name('my_names_app')->from_string(<<EOF)->migrate;
  -- 1 up
  create table names (id integer primary key autoincrement, name text);
  -- 1 down
  drop table names;
  EOF

  # Use migrations to drop and recreate the table
  $sql->migrations->migrate(0)->migrate;

  # Get a database handle from the cache for multiple queries
  my $db = $sql->db;

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

  # Insert a few rows in a transaction with SQL and placeholders
  eval {
    my $tx = $db->begin;
    $db->query('insert into names (name) values (?)', 'Sara');
    $db->query('insert into names (name) values (?)', 'Stefan');
    $tx->commit;
  };
  say $@ if $@;

  # Insert another row with SQL::Abstract and return the generated id
  say $db->insert('names', {name => 'Daniel'})->last_insert_id;
  
  # JSON roundtrip
  say $db->query('select ? as foo', {json => {bar => 'baz'}})
    ->expand(json => 'foo')->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 with SQL::Abstract
  say $_->{name} for $db->select('names')->hashes->each;

DESCRIPTION

Mojo::SQLite is a tiny wrapper around DBD::SQLite that makes SQLite 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. And you can handle connection timeouts gracefully by holding on to them only for short amounts of time.

  use Mojolicious::Lite;
  use Mojo::SQLite;

  helper sqlite => sub { state $sql = Mojo::SQLite->new('sqlite:test.db') };

  get '/' => sub {
    my $c  = shift;
    my $db = $c->sqlite->db;
    $c->render(json => $db->query('select datetime("now","localtime") as now')->hash);
  };

  app->start;

In this example application, we create a sqlite helper to store a Mojo::SQLite object. Our action calls that helper and uses the method "db" in Mojo::SQLite to dequeue a Mojo::SQLite::Database object from the connection pool. Then we use the method "query" in Mojo::SQLite::Database to execute an SQL statement, which returns a Mojo::SQLite::Results object. And finally we call the method "hash" in Mojo::SQLite::Results to retrieve the first row as a hash reference.

All I/O and queries are performed synchronously. However, the "Write-Ahead Log" journal is enabled for all connections, allowing multiple processes to read and write concurrently to the same database file (but only one can write at a time). You can prevent this mode from being enabled by passing the option no_wal. See http://sqlite.org/wal.html for more information.

  # Performed concurrently
  my $pid = fork || die $!;
  say $sql->db->query('select datetime("now","localtime") as time')->hash->{time};
  exit unless $pid;

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

Any database errors will throw an exception as RaiseError is automatically enabled, so use eval or Try::Tiny to catch them. This makes transactions with "begin" in Mojo::SQLite::Database easy.

While passing a file path of :memory: (or a custom "dsn" with mode=memory) will create a temporary database, in-memory databases cannot be shared between connections, so subsequent calls to "db" may return connections to completely different databases. For a temporary database that can be shared between connections and processes, pass a file path of :temp: to store the database in a temporary directory (this is the default), or consider constructing a temporary directory yourself with File::Temp if you need to reuse the filename. A temporary directory allows SQLite to create additional temporary files safely.

  use File::Spec::Functions 'catfile';
  use File::Temp;
  use Mojo::SQLite;
  my $tempdir = File::Temp->newdir; # Deleted when object goes out of scope
  my $tempfile = catfile $tempdir, 'test.db';
  my $sql = Mojo::SQLite->new->from_filename($tempfile);

EXAMPLES

This distribution also contains a well-structured example blog application you can use for inspiration. This application shows how to apply the MVC design pattern in practice.

EVENTS

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

connection

  $sql->on(connection => sub {
    my ($sql, $dbh) = @_;
    $dbh->do('pragma journal_size_limit=1000000');
  });

Emitted when a new database connection has been established.

ATTRIBUTES

Mojo::SQLite implements the following attributes.

abstract

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

SQL::Abstract object used to generate CRUD queries for Mojo::SQLite::Database, defaults to setting name_sep to . and quote_char to ".

  # Generate WHERE clause and bind values
  my($stmt, @bind) = $sql->abstract->where({foo => 'bar', baz => 'yada'});

auto_migrate

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

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

database_class

  my $class = $sql->database_class;
  $sql      = $sql->database_class('MyApp::Database');

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

dsn

  my $dsn = $sql->dsn;
  $sql    = $sql->dsn('dbi:SQLite:uri=file:foo.db');

Data source name, defaults to dbi:SQLite:dbname= followed by a path to a temporary file.

max_connections

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

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

migrations

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

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

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

options

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

Options for database handles, defaults to activating sqlite_unicode, AutoCommit, AutoInactiveDestroy as well as RaiseError and deactivating PrintError. Note that AutoCommit and RaiseError are considered mandatory, so deactivating them would be very dangerous. See "ATTRIBUTES COMMON TO ALL HANDLES" in DBI and "DRIVER PRIVATE ATTRIBUTES" in DBD::SQLite for more information on available options.

pubsub

This attribute is DEPRECATED.

METHODS

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

new

  my $sql = Mojo::SQLite->new;
  my $sql = Mojo::SQLite->new('file:test.db);
  my $sql = Mojo::SQLite->new('sqlite:test.db');

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

  # Customize configuration further
  my $sql = Mojo::SQLite->new->dsn('dbi:SQLite:dbname=test.db');
  my $sql = Mojo::SQLite->new->dsn('dbi:SQLite:uri=file:test.db?mode=memory');

  # Pass filename directly
  my $sql = Mojo::SQLite->new->from_filename($filename);

db

  my $db = $sql->db;

Get a database object based on "database_class" (which is usually Mojo::SQLite::Database) for a cached or newly established database connection. The DBD::SQLite 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 $sql->db->select('accounts')
    ->hashes->reduce(sub { $a->{money} + $b->{money} });

from_filename

  $sql = $sql->from_filename('C:\\Documents and Settings\\foo & bar.db', $options);

Parse database filename directly. Unlike "from_string", the filename is parsed as a local filename and not a URL. A hashref of "options" may be passed as the second argument.

  # Absolute filename
  $sql->from_filename('/home/fred/data.db');

  # Relative to current directory
  $sql->from_filename('data.db');

  # Temporary file database (default)
  $sql->from_filename(':temp:');

  # In-memory temporary database (single connection only)
  my $db = $sql->from_filename(':memory:')->db;

  # Additional options
  $sql->from_filename($filename, { PrintError => 1 });
  
  # Readonly connection without WAL mode
  $sql->from_filename($filename, { ReadOnly => 1, no_wal => 1 });

from_string

  $sql = $sql->from_string('test.db');
  $sql = $sql->from_string('file:test.db');
  $sql = $sql->from_string('file:///C:/foo/bar.db');
  $sql = $sql->from_string('sqlite:C:%5Cfoo%5Cbar.db');

Parse configuration from connection string. Connection strings are parsed as URLs, so you should construct them using a module like Mojo::URL, URI::file, or URI::db. For portability on non-Unix-like systems, either construct the URL with the sqlite scheme, or use "new" in URI::file to construct a URL with the file scheme. A URL with no scheme will be parsed as a file URL, and file URLs are parsed according to the current operating system. If specified, the hostname must be localhost. If the URL has a query string, it will be parsed and applied to "options".

  # Absolute filename
  $sql->from_string('sqlite:////home/fred/data.db');
  $sql->from_string('sqlite://localhost//home/fred/data.db');
  $sql->from_string('sqlite:/home/fred/data.db');
  $sql->from_string('file:///home/fred/data.db');
  $sql->from_string('file://localhost/home/fred/data.db');
  $sql->from_string('file:/home/fred/data.db');
  $sql->from_string('///home/fred/data.db');
  $sql->from_string('//localhost/home/fred/data.db');
  $sql->from_string('/home/fred/data.db');

  # Relative to current directory
  $sql->from_string('sqlite:data.db');
  $sql->from_string('file:data.db');
  $sql->from_string('data.db');

  # Connection string must be a valid URL
  $sql->from_string(Mojo::URL->new->scheme('sqlite')->path($filename));
  $sql->from_string(URI::db->new->Mojo::Base::tap(engine => 'sqlite')->Mojo::Base::tap(dbname => $filename));
  $sql->from_string(URI::file->new($filename));

  # Temporary file database (default)
  $sql->from_string(':temp:');

  # In-memory temporary database (single connection only)
  my $db = $sql->from_string(':memory:')->db;

  # Additional options
  $sql->from_string('data.db?PrintError=1&sqlite_allow_multiple_statements=1');
  $sql->from_string(Mojo::URL->new->scheme('sqlite')->path($filename)->query(sqlite_see_if_its_a_number => 1));
  $sql->from_string(URI::file->new($filename)->Mojo::Base::tap(query_form => {PrintError => 1}));

  # Readonly connection without WAL mode
  $sql->from_string('data.db?ReadOnly=1&no_wal=1');

DEBUGGING

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

  DBI_TRACE=1
  DBI_TRACE=15
  DBI_TRACE=SQL

REFERENCE

This is the class hierarchy of the Mojo::SQLite distribution.

BUGS

Report any issues on the public bugtracker.

AUTHOR

Dan Book, dbook@cpan.org

CREDITS

Sebastian Riedel, author of Mojo::Pg, which this distribution is based on.

COPYRIGHT AND LICENSE

Copyright 2015, Dan Book.

This library is free software; you may redistribute it and/or modify it under the terms of the Artistic License version 2.0.

SEE ALSO

Mojolicious, Mojo::Pg, DBD::SQLite