1DBIx::Class::Schema::VeUrsseironCeodn(t3r)ibuted Perl DoDcBuImxe:n:tCaltaisosn::Schema::Versioned(3)
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NAME

6       DBIx::Class::Schema::Versioned - DBIx::Class::Schema plugin for Schema
7       upgrades
8

SYNOPSIS

10         package MyApp::Schema;
11         use base qw/DBIx::Class::Schema/;
12
13         our $VERSION = 0.001;
14
15         # load MyApp::Schema::CD, MyApp::Schema::Book, MyApp::Schema::DVD
16         __PACKAGE__->load_classes(qw/CD Book DVD/);
17
18         __PACKAGE__->load_components(qw/Schema::Versioned/);
19         __PACKAGE__->upgrade_directory('/path/to/upgrades/');
20

DESCRIPTION

22       This module provides methods to apply DDL changes to your database
23       using SQL diff files. Normally these diff files would be created using
24       "create_ddl_dir" in DBIx::Class::Schema.
25
26       A table called dbix_class_schema_versions is created and maintained by
27       the module. This is used to determine which version your database is
28       currently at.  Similarly the $VERSION in your DBIC schema class is used
29       to determine the current DBIC schema version.
30
31       The upgrade is initiated manually by calling "upgrade" on your schema
32       object, this will attempt to upgrade the database from its current
33       version to the current schema version using a diff from your
34       upgrade_directory. If a suitable diff is not found then no upgrade is
35       possible.
36

SEE ALSO

38       DBIx::Class::DeploymentHandler is a much more powerful alternative to
39       this module.  Examples of things it can do that this module cannot do
40       include
41
42       ·   Downgrades in addition to upgrades
43
44       ·   Multiple sql files per upgrade/downgrade/install
45
46       ·   Perl scripts allowed for upgrade/downgrade/install
47
48       ·   Just one set of files needed for upgrade, unlike this module where
49           one might need to generate "factorial(scalar @versions)"
50

GETTING STARTED

52       Firstly you need to setup your schema class as per the "SYNOPSIS", make
53       sure you have specified an upgrade_directory and an initial $VERSION.
54
55       Then you'll need two scripts, one to create DDL files and diffs and
56       another to perform upgrades. Your creation script might look like a bit
57       like this:
58
59         use strict;
60         use Pod::Usage;
61         use Getopt::Long;
62         use MyApp::Schema;
63
64         my ( $preversion, $help );
65         GetOptions(
66           'p|preversion:s'  => \$preversion,
67         ) or die pod2usage;
68
69         my $schema = MyApp::Schema->connect(
70           $dsn,
71           $user,
72           $password,
73         );
74         my $sql_dir = './sql';
75         my $version = $schema->schema_version();
76         $schema->create_ddl_dir( 'MySQL', $version, $sql_dir, $preversion );
77
78       Then your upgrade script might look like so:
79
80         use strict;
81         use MyApp::Schema;
82
83         my $schema = MyApp::Schema->connect(
84           $dsn,
85           $user,
86           $password,
87         );
88
89         if (!$schema->get_db_version()) {
90           # schema is unversioned
91           $schema->deploy();
92         } else {
93           $schema->upgrade();
94         }
95
96       The script above assumes that if the database is unversioned then it is
97       empty and we can safely deploy the DDL to it. However things are not
98       always so simple.
99
100       if you want to initialise a pre-existing database where the DDL is not
101       the same as the DDL for your current schema version then you will need
102       a diff which converts the database's DDL to the current DDL. The best
103       way to do this is to get a dump of the database schema (without data)
104       and save that in your SQL directory as version 0.000 (the filename must
105       be as with "ddl_filename" in DBIx::Class::Schema) then create a diff
106       using your create DDL script given above from version 0.000 to the
107       current version. Then hand check and if necessary edit the resulting
108       diff to ensure that it will apply. Once you have done all that you can
109       do this:
110
111         if (!$schema->get_db_version()) {
112           # schema is unversioned
113           $schema->install("0.000");
114         }
115
116         # this will now apply the 0.000 to current version diff
117         $schema->upgrade();
118
119       In the case of an unversioned database the above code will create the
120       dbix_class_schema_versions table and write version 0.000 to it, then
121       upgrade will then apply the diff we talked about creating in the
122       previous paragraph and then you're good to go.
123

METHODS

125   upgrade_directory
126       Use this to set the directory your upgrade files are stored in.
127
128   backup_directory
129       Use this to set the directory you want your backups stored in (note
130       that backups are disabled by default).
131
132   install
133       Arguments: $db_version
134
135       Call this to initialise a previously unversioned database. The table
136       'dbix_class_schema_versions' will be created which will be used to
137       store the database version.
138
139       Takes one argument which should be the version that the database is
140       currently at. Defaults to the return value of "schema_version".
141
142       See "GETTING STARTED" for more details.
143
144   deploy
145       Same as "deploy" in DBIx::Class::Schema but also calls "install".
146
147   create_upgrade_path
148       Arguments: { upgrade_file => $file }
149
150       Virtual method that should be overridden to create an upgrade file.
151       This is useful in the case of upgrading across multiple versions to
152       concatenate several files to create one upgrade file.
153
154       You'll probably want the db_version retrieved via $self->get_db_version
155       and the schema_version which is retrieved via $self->schema_version
156
157   ordered_schema_versions
158       Return Value: a list of version numbers, ordered from lowest to highest
159
160       Virtual method that should be overridden to return an ordered list of
161       schema versions. This is then used to produce a set of steps to upgrade
162       through to achieve the required schema version.
163
164       You may want the db_version retrieved via $self->get_db_version and the
165       schema_version which is retrieved via $self->schema_version
166
167   upgrade
168       Call this to attempt to upgrade your database from the version it is at
169       to the version this DBIC schema is at. If they are the same it does
170       nothing.
171
172       It will call "ordered_schema_versions" to retrieve an ordered list of
173       schema versions (if ordered_schema_versions returns nothing then it is
174       assumed you can do the upgrade as a single step). It then iterates
175       through the list of versions between the current db version and the
176       schema version applying one update at a time until all relevant updates
177       are applied.
178
179       The individual update steps are performed by using
180       "upgrade_single_step", which will apply the update and also update the
181       dbix_class_schema_versions table.
182
183   upgrade_single_step
184       Arguments: db_version - the version currently within the db
185       Arguments: target_version - the version to upgrade to
186
187       Call this to attempt to upgrade your database from the db_version to
188       the target_version. If they are the same it does nothing.
189
190       It requires an SQL diff file to exist in your upgrade_directory,
191       normally you will have created this using "create_ddl_dir" in
192       DBIx::Class::Schema.
193
194       If successful the dbix_class_schema_versions table is updated with the
195       target_version.
196
197       This method may be called repeatedly by the upgrade method to upgrade
198       through a series of updates.
199
200   do_upgrade
201       This is an overwritable method used to run your upgrade. The freeform
202       method allows you to run your upgrade any way you please, you can call
203       "run_upgrade" any number of times to run the actual SQL commands, and
204       in between you can sandwich your data upgrading. For example, first run
205       all the CREATE commands, then migrate your data from old to new
206       tables/formats, then issue the DROP commands when you are finished.
207       Will run the whole file as it is by default.
208
209   run_upgrade
210        $self->run_upgrade(qr/create/i);
211
212       Runs a set of SQL statements matching a passed in regular expression.
213       The idea is that this method can be called any number of times from
214       your "do_upgrade" method, running whichever commands you specify via
215       the regex in the parameter. Probably won't work unless called from the
216       overridable do_upgrade method.
217
218   apply_statement
219       Takes an SQL statement and runs it. Override this if you want to handle
220       errors differently.
221
222   get_db_version
223       Returns the version that your database is currently at. This is
224       determined by the values in the dbix_class_schema_versions table that
225       "upgrade" and "install" write to.
226
227   schema_version
228       Returns the current schema class' $VERSION
229
230   backup
231       This is an overwritable method which is called just before the upgrade,
232       to allow you to make a backup of the database. Per default this method
233       attempts to call "$self->storage->backup", to run the standard backup
234       on each database type.
235
236       This method should return the name of the backup file, if appropriate..
237
238       This method is disabled by default. Set $schema->do_backup(1) to enable
239       it.
240
241   connection
242       Overloaded method. This checks the DBIC schema version against the DB
243       version and warns if they are not the same or if the DB is unversioned.
244       It also provides compatibility between the old versions table
245       (SchemaVersions) and the new one (dbix_class_schema_versions).
246
247       To avoid the checks on connect, set the environment var
248       DBIC_NO_VERSION_CHECK or alternatively you can set the ignore_version
249       attr in the forth argument like so:
250
251         my $schema = MyApp::Schema->connect(
252           $dsn,
253           $user,
254           $password,
255           { ignore_version => 1 },
256         );
257

FURTHER QUESTIONS?

259       Check the list of additional DBIC resources.
260
262       This module is free software copyright by the DBIx::Class (DBIC)
263       authors. You can redistribute it and/or modify it under the same terms
264       as the DBIx::Class library.
265
266
267
268perl v5.32.0                      2020-07-28 DBIx::Class::Schema::Versioned(3)
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