NAME

       Mojo::Pg::Migrations - Migrations

SYNOPSIS

         use Mojo::Pg::Migrations;

         my $migrations = Mojo::Pg::Migrations->new(pg => $pg);
         $migrations->from_file('/home/sri/migrations.sql')->migrate;

DESCRIPTION

       Mojo::Pg::Migrations is used by Mojo::Pg to allow database schemas to evolve easily over
       time. A migration file is just a collection of sql blocks, with one or more statements,
       separated by comments of the form "-- VERSION UP/DOWN".

         -- 1 up
         CREATE TABLE messages (message TEXT);
         INSERT INTO messages VALUES ('I ♥ Mojolicious!');
         -- 1 down
         DROP TABLE messages;

         -- 2 up (...you can comment freely here...)
         CREATE TABLE stuff (whatever INT);
         -- 2 down
         DROP TABLE stuff;

       The idea is to let you migrate from any version, to any version, up and down. Migrations
       are very safe, because they are performed in transactions and only one can be performed at
       a time. If a single statement fails, the whole migration will fail and get rolled back.
       Every set of migrations has a "name", which is stored together with the currently active
       version in an automatically created table named "mojo_migrations".

ATTRIBUTES

       Mojo::Pg::Migrations implements the following attributes.

   name
         my $name    = $migrations->name;
         $migrations = $migrations->name('foo');

       Name for this set of migrations, defaults to "migrations".

   pg
         my $pg      = $migrations->pg;
         $migrations = $migrations->pg(Mojo::Pg->new);

       Mojo::Pg object these migrations belong to. Note that this attribute is weakened.

METHODS

       Mojo::Pg::Migrations inherits all methods from Mojo::Base and implements the following new
       ones.

   active
         my $version = $migrations->active;

       Currently active version.

   from_data
         $migrations = $migrations->from_data;
         $migrations = $migrations->from_data('main');
         $migrations = $migrations->from_data('main', 'file_name');

       Extract migrations from a file in the DATA section of a class with "data_section" in
       Mojo::Loader, defaults to using the caller class and "name".

         __DATA__
         @@ migrations
         -- 1 up
         CREATE TABLE messages (message TEXT);
         INSERT INTO messages VALUES ('I ♥ Mojolicious!');
         -- 1 down
         DROP TABLE messages;

   from_dir
         $migrations = $migrations->from_dir('/home/sri/migrations');

       Extract migrations from a directory tree where each versioned migration is in a directory,
       named for the version, and each migration has one or both of the files named "up.sql" or
       "down.sql".

         migrations/1/up.sql
         migrations/1/down.sql
         migrations/2/up.sql
         migrations/3/up.sql
         migrations/3/down.sql

   from_file
         $migrations = $migrations->from_file('/home/sri/migrations.sql');

       Extract migrations from a file.

   from_string
         $migrations = $migrations->from_string(
           '-- 1 up
            CREATE TABLE foo (bar INT);
            -- 1 down
            DROP TABLE foo;'
         );

       Extract migrations from string.

   latest
         my $version = $migrations->latest;

       Latest version available.

   migrate
         $migrations = $migrations->migrate;
         $migrations = $migrations->migrate(3);

       Migrate from "active" to a different version, up or down, defaults to using "latest". All
       version numbers need to be positive, with version 0 representing an empty database.

         # Reset database
         $migrations->migrate(0)->migrate;

   sql_for
         my $sql = $migrations->sql_for(5, 10);

       Get SQL to migrate from one version to another, up or down.

DEBUGGING

       You can set the "MOJO_MIGRATIONS_DEBUG" environment variable to get some advanced
       diagnostics information printed to "STDERR".

         MOJO_MIGRATIONS_DEBUG=1

SEE ALSO

       Mojo::Pg, Mojolicious::Guides, <https://mojolicious.org>.