Mojo::SQLite(3pm)

🎀 NAME 🎀

Mojo::SQLite — a tiny Mojolicious wrapper for SQLite. This is the Mojo::SQLite(3pm) page from User Contributed Perl Documentation, and it's literally your new fave little SQLite bestie.

💻 SYNOPSIS 💻

okay bestie, here's the whole vibe in code form:

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 (https://www.sqlite.org/) a lot of fun to use with the Mojolicious (https://mojolico.us) real-time web framework. Use all SQL features (http://sqlite.org/lang.html) SQLite has to offer, generate CRUD queries from data structures, and manage your database schema with migrations. Periodt.

🧚 BASICS 🧚

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 ($c) {
  my $db = $c->sqlite->db;
  $c->render(json => $db->query(q{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 (http://www.postgresql.org/docs/current/static/sql.html), 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, and SQLite's default journal mode only supports concurrent reads from multiple processes while the database is not being written. The "Write-Ahead Log" journal mode allows multiple processes to read and write concurrently to the same database file (but only one can write at a time). WAL mode is enabled by the wal_mode option, currently enabled by default, and persists when opening that same database in the future.

# Performed concurrently (concurrent with writing only with WAL journaling mode)
my $pid = fork || die $!;
say $sql->db->query(q{select datetime('now','localtime') as time})->hash->{time};
exit unless $pid;

The no_wal option prevents WAL mode from being enabled in new databases but doesn't affect databases where it has already been enabled. wal_mode may not be set by default in a future release. See http://sqlite.org/wal.html and "journal_mode" in DBD::SQLite for more information.

The double-quoted string literal misfeature (https://sqlite.org/quirks.html#double_quoted_string_literals_are_accepted) is disabled for all connections since Mojo::SQLite 3.003; use single quotes for string literals and double quotes for identifiers, as is normally recommended.

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 (https://www.sqlite.org/tempfiles.html) 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 (https://github.com/Grinnz/Mojo-SQLite/tree/master/examples/blog) 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

$sql->on(connection => sub ($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 a SQL::Abstract::Pg object with name_sep set to "." and quote_char set to " (a double quote).

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

SQL::Abstract::Pg provides additional features to the SQL::Abstract query methods in Mojo::SQLite::Database such as -json and limit/offset. The for feature is not applicable to SQLite queries.

$sql->db->select(['some_table', ['other_table', foo_id => 'id']],
  ['foo', [bar => 'baz'], \q{datetime('now') as dt}],
  {foo => 'value'},
  {order_by => 'foo', limit => 10, offset => 5, group_by => ['foo'], having => {baz => 'value'}});

# Upsert supported since SQLite 3.24.0
$sql->db->insert('some_table', {name => $name, value => $value},
  {on_conflict => [name => {value => \'"excluded"."value"'}]});

🧬 auto_migrate

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

Automatically migrate to the latest database schema with migrations, as soon as db has been called for the first time.

🏷️ 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 1.

🚚 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 setting sqlite_string_mode to DBD_SQLITE_STRING_MODE_UNICODE_FALLBACK, setting AutoCommit, AutoInactiveDestroy and 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.

👯 parent

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

Another Mojo::SQLite object to use for connection management, instead of establishing and caching our own database connections.

💅 METHODS 💅

Okay so Mojo::SQLite inherits every single method from Mojo::EventEmitter, and then it serves up these new ones of its own. Periodt. 💖

---

✨ new ✨

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

Construct a shiny new Mojo::SQLite object, and it parses the connection string with from_string if necessary. Lowkey iconic. 🎀

# 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. Slay, but briefly. 💅

# 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. It’s giving “just give me the file, bestie.” 🦋

# 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 });

# Strict unicode strings and WAL mode
use DBD::SQLite::Constants ':dbd_sqlite_string_mode';
$sql->from_filename($filename, { sqlite_string_mode => DBD_SQLITE_STRING_MODE_UNICODE_STRICT, wal_mode => 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');
$sql = $sql->from_string(Mojo::SQLite->new);

Parse configuration from a connection string, or use another Mojo::SQLite object as parent. 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. Iykyk. 🌈

# 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');

# String unicode strings and WAL mode
use DBD::SQLite::Constants ':dbd_sqlite_string_mode';
$sql->from_string(Mojo::URL->new->scheme('sqlite')->path('data.db')
  ->query(sqlite_string_mode => DBD_SQLITE_STRING_MODE_UNICODE_STRICT, wal_mode => 1));

---

🐞 DEBUGGING 🐞

You can set the DBI_TRACE environment variable to get some advanced diagnostics information printed by DBI. Detective mode: activated. 🔥

DBI_TRACE=1
DBI_TRACE=15
DBI_TRACE=SQL

---

📚 REFERENCE 📚

This is the class hierarchy of the Mojo::SQLite distribution. Main character lineup, honestly. 👑

• Mojo::SQLite
• Mojo::SQLite::Database
• Mojo::SQLite::Migrations
• Mojo::SQLite::Results
• Mojo::SQLite::Transaction

---

🐛 BUGS 🐛

Report any issues on the public bugtracker. No gatekeeping, bestie. 🫶

---

👑 AUTHOR 👑

Dan Book, dbook@cpan.org

---

🌈 CREDITS 🌈

Sebastian Riedel, author of Mojo::Pg, which this distribution is based on. Respect the blueprint. 💜

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📜 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.

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🦋 SEE ALSO 🦋

Mojolicious, Mojo::Pg, DBD::SQLite

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That’s a wrap, bestie 🫶 — footer deets: perl v5.42.0, dated 2022-03-23, and it’s the Mojo::SQLite(3pm) page. 💖