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15 Mar 2022 12:13:59 UTC
- Distribution: Mojo-Pg
- Module version: 4.27
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- License: artistic_2
- Perl: v5.16.0
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- NAME
- SYNOPSIS
- DESCRIPTION
- BASICS
- GROWING
- EXAMPLES
- EVENTS
- ATTRIBUTES
- METHODS
- DEBUGGING
- API
- AUTHOR
- CREDITS
- COPYRIGHT AND LICENSE
- SEE ALSO
NAME
Mojo::Pg - Mojolicious ♥ PostgreSQL
SYNOPSIS
use Mojo::Pg; # Use a PostgreSQL connection string for configuration my $pg = Mojo::Pg->new('postgresql://postgres@/test'); # Select the server version say $pg->db->query('SELECT VERSION() AS version')->hash->{version}; # Use migrations to create a table $pg->migrations->name('my_names_app')->from_string(<<EOF)->migrate; -- 1 up CREATE TABLE names (id SERIAL PRIMARY KEY, name TEXT); -- 1 down DROP TABLE names; EOF # Use migrations to drop and recreate the table $pg->migrations->migrate(0)->migrate; # Get a database handle from the cache for multiple queries my $db = $pg->db; # Use SQL::Abstract to generate simple CRUD queries for you $db->insert('names', {name => 'Isabell'}); my $id = $db->select('names', ['id'], {name => 'Isabell'})->hash->{id}; $db->update('names', {name => 'Belle'}, {id => $id}); $db->delete('names', {name => 'Belle'}); # 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'}, {returning => 'id'})->hash->{id}; # JSON roundtrip say $db->query('SELECT ?::JSON AS foo', {json => {bar => 'baz'}}) ->expand->hash->{foo}{bar}; # Select all rows blocking with SQL::Abstract say $_->{name} for $db->select('names')->hashes->each; # Select all rows non-blocking with SQL::Abstract $db->select('names' => sub ($db, $err, $results) { die $err if $err; say $_->{name} for $results->hashes->each; }); Mojo::IOLoop->start unless Mojo::IOLoop->is_running; # Concurrent non-blocking queries (synchronized with promises) my $now = $pg->db->query_p('SELECT NOW() AS now'); my $names = $pg->db->query_p('SELECT * FROM names'); Mojo::Promise->all($now, $names)->then(sub ($now, $names) { say $now->[0]->hash->{now}; say $_->{name} for $names->[0]->hashes->each; })->catch(sub ($err) { warn "Something went wrong: $err"; })->wait; # Send and receive notifications non-blocking $pg->pubsub->listen(foo => sub ($pubsub, $payload) { say "foo: $payload"; $pubsub->notify(bar => $payload); }); $pg->pubsub->listen(bar => sub ($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 a lot of fun to use with the Mojolicious real-time web framework. Perform queries blocking and non-blocking, use all SQL features PostgreSQL has to offer, generate CRUD queries from data structures, manage your database schema with migrations and build scalable real-time web applications with the publish/subscribe pattern.
BASICS
Database and statement handles are cached automatically, and will be reused transparently to increase performance. You can handle connection timeouts gracefully by holding on to them only for short amounts of time.
use Mojolicious::Lite -signatures; use Mojo::Pg; helper pg => sub { state $pg = Mojo::Pg->new('postgresql://postgres@/test') }; get '/' => sub ($c) { my $db = $c->pg->db; $c->render(json => $db->query('SELECT NOW() AS now')->hash); }; app->start;
In this example application, we create a
pg
helper to store a Mojo::Pg object. Our action calls that helper and uses the method "db" in Mojo::Pg to dequeue a Mojo::Pg::Database object from the connection pool. Then we use the method "query" in Mojo::Pg::Database to execute an SQL statement, which returns a Mojo::Pg::Results object. And finally we call the method "hash" in Mojo::Pg::Results to retrieve the first row as a hash reference.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) $pg->db->query('SELECT PG_SLEEP(5)' => sub ($db, $err, $results) {...}); $pg->db->query('SELECT PG_SLEEP(5)' => sub ($db, $err, $results) {...});
All cached database handles will be reset automatically if a new process has been forked, this allows multiple processes to share the same Mojo::Pg object safely.
GROWING
And as your application grows, you can move queries into model classes.
package MyApp::Model::Time; use Mojo::Base -base, -signatures; has 'pg'; sub now ($self) { return $self->pg->db->query('SELECT NOW() AS now')->hash; } 1;
Which get integrated into your application with helpers.
use Mojolicious::Lite -signatures; use Mojo::Pg; use MyApp::Model::Time; helper pg => sub { state $pg = Mojo::Pg->new('postgresql://postgres@/test') }; helper time => sub { state $time = MyApp::Model::Time->new(pg => shift->pg) }; get '/' => sub ($c) { $c->render(json => $c->time->now); }; app->start;
EXAMPLES
This distribution also contains two great example applications you can use for inspiration. The minimal chat application will show you how to scale WebSockets to multiple servers, and the well-structured blog application how to apply the MVC design pattern in practice.
EVENTS
Mojo::Pg inherits all events from Mojo::EventEmitter and can emit the following new ones.
connection
$pg->on(connection => sub ($pg, $dbh) { ... });
Emitted when a new database connection has been established.
$pg->on(connection => sub ($pg, $dbh) { $dbh->do('SET search_path TO my_schema'); });
ATTRIBUTES
Mojo::Pg implements the following attributes.
abstract
my $abstract = $pg->abstract; $pg = $pg->abstract(SQL::Abstract::Pg->new);
SQL::Abstract::Pg object used to generate CRUD queries for Mojo::Pg::Database, defaults to enabling
array_datatypes
and settingname_sep
to.
andquote_char
to"
.# Generate WHERE clause and bind values my($stmt, @bind) = $pg->abstract->where({foo => 'bar', baz => 'yada'});
auto_migrate
my $bool = $pg->auto_migrate; $pg = $pg->auto_migrate($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 = $pg->database_class; $pg = $pg->database_class('MyApp::Database');
Class to be used by "db", defaults to Mojo::Pg::Database. Note that this class needs to have already been loaded before "db" is called.
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
1
.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 asRaiseError
and deactivatingPrintError
as well asPrintWarn
. Note thatAutoCommit
andRaiseError
are considered mandatory, so deactivating them would be very dangerous.parent
my $parent = $pg->parent; $pg = $pg->parent(Mojo::Pg->new);
Another Mojo::Pg object to use for connection management, instead of establishing and caching our own database connections.
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 $pg->pubsub->listen(news => sub ($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 my $pg = Mojo::Pg->new('postgresql:///test')->search_path(['test_one']); $pg->db->query('DROP SCHEMA IF EXISTS test_one CASCADE'); $pg->db->query('CREATE SCHEMA test_one'); ... $pg->db->query('DROP SCHEMA test_one CASCADE');
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 a database object based on "database_class" (which is usually Mojo::Pg::Database) 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->select('accounts')->hashes->reduce(sub { $a->{money} + $b->{money} });
from_string
$pg = $pg->from_string('postgresql://postgres@/test'); $pg = $pg->from_string(Mojo::Pg->new);
Parse configuration from connection string or use another Mojo::Pg object as "parent".
# 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'); # Short scheme, username, password, host and database $pg->from_string('postgres://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'); # Username, database, an option and search_path $pg->from_string('postgres://sri@/db6?&PrintError=1&search_path=test_schema');
new
my $pg = Mojo::Pg->new; my $pg = Mojo::Pg->new('postgresql://postgres@/test'); my $pg = Mojo::Pg->new(Mojo::Pg->new);
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');
reset
$pg = $pg->reset;
Reset connection cache.
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
API
This is the class hierarchy of the Mojo::Pg distribution.
AUTHOR
Sebastian Riedel,
sri@cpan.org
.CREDITS
In alphabetical order:
Christopher Eveland
Dan Book
Flavio Poletti
Hernan Lopes
Joel Berger
Matt S Trout
Peter Rabbitson
William Lindley
COPYRIGHT AND LICENSE
Copyright (C) 2014-2022, Sebastian Riedel and others.
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/mojolicious/mojo-pg, Mojolicious::Guides, https://mojolicious.org.
Module Install Instructions
To install Mojo::Pg, copy and paste the appropriate command in to your terminal.
cpanm Mojo::Pg
perl -MCPAN -e shell install Mojo::Pg
For more information on module installation, please visit the detailed CPAN module installation guide.