/ 
DBIx-Migration-0.25
River stage one • 1 direct dependent • 1 total dependent
/ DBIx::Migration::Pg

NAME

DBIx::Migration::Pg - Seamless PostgreSQL database schema up- and downgrades

SYNOPSIS

use DBIx::Migration::Pg ();

# Create Pg migration object
my $m = DBIx::Migration::Pg->new(
  dsn            => 'dbi:Pg:dbname=myapp.db;host=localhost;port=5432;user=postgres',
  tracking_table => 'myapp_migration',
  managed_schema => 'myapp'
);

DESCRIPTION

PostgreSQL databases support schemas. A schema can contain different kind of named objects like for example tables, data types, functions, and so on.

An application that wants to use a PostgreSQL database can reserve one or more schemas for use. From the perspective of a migration framework these schemas are called managed schemas. The DBIx::Migration::Pg class can cope with single managed schema applications. The default managed schema is the public schema. This schema usually exists. Considering the use case that more than one application uses the same PostgreSQL database, the default value should be changed for each application. At creation time of a DBIx::Migration::Pg object you may use the managed_schema attribute to overwrite the default managed schema.

For a PostgreSQL database you may set a tracking schema (the schema of your tracking table) too. By default the tracking schema is the public schema. If you neither change this default nor the default of the tracking table a clash will occur if more than one application uses the same PostgreSQL database. At creation time of a DBIx::Migration::Pg object you should either overwrite the tracking_table attribute and/or the tracking_schema attribute.

ACCESSORS

$self->do_before

Get PostgreSQL database specific default list of SQL statements that are executed before the migration transaction begins. The default list contains a single statement that assigns the managed schema to the search_path option.

$self->do_while

Get PostgreSQL database specific default list of SQL statements that are executed immediately after the migration transaction was enabled. The default list contains a single statement that locks the tracking table.

$self->managed_schema

Get schema that your application refers to.

$self->tracking_schema

Get schema that the tracking table belongs to.

$self->placeholders

Get map of placeholders. The map contains a single key value pair. The dbix_migration_managed_schema key refers to the managed_schema value.

METHODS

$self->create_tracking_table

Create the tracking table if it does not exist yet. Beforehand create the tracking schema if it does not exist yet.

$self->quoted_tracking_table

Quote tracking table taking the tracking schema into consideration.

COMPARISONS

There are more PostgreSQL database migration libraries on the CPAN. This chapter tries to compare some of them. The content is work in progress.

|                         | DBIx::Migration                 | App::Sqitch            |
+-------------------------+---------------------------------+------------------------+
| change                  | migration                       | change                 |
| SQL script types        | up, down                        | deploy, revert, verify |
| tracking                | tracking table                  | registry tables        |
| dependency relationship | linear (numbered consecutively) | tree like (requires)   |

SEE ALSO