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.\" ========================================================================
.\"
.IX Title "Mojo::Pg::Migrations 3pm"
.TH Mojo::Pg::Migrations 3pm "2022-03-19" "perl v5.34.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
Mojo::Pg::Migrations \- Migrations
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use Mojo::Pg::Migrations;
\&
\&  my $migrations = Mojo::Pg::Migrations\->new(pg => $pg);
\&  $migrations\->from_file(\*(Aq/home/sri/migrations.sql\*(Aq)\->migrate;
.Ve
.SH "DESCRIPTION"
.IX Header "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 \f(CW\*(C`\-\- VERSION
UP/DOWN\*(C'\fR.
.PP
.Vb 5
\&  \-\- 1 up
\&  CREATE TABLE messages (message TEXT);
\&  INSERT INTO messages VALUES (\*(AqI ♥ Mojolicious!\*(Aq);
\&  \-\- 1 down
\&  DROP TABLE messages;
\&
\&  \-\- 2 up (...you can comment freely here...)
\&  CREATE TABLE stuff (whatever INT);
\&  \-\- 2 down
\&  DROP TABLE stuff;
.Ve
.PP
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 \*(L"name\*(R", which is stored together with the currently
active version in an automatically created table named \f(CW\*(C`mojo_migrations\*(C'\fR.
.SH "ATTRIBUTES"
.IX Header "ATTRIBUTES"
Mojo::Pg::Migrations implements the following attributes.
.SS "name"
.IX Subsection "name"
.Vb 2
\&  my $name    = $migrations\->name;
\&  $migrations = $migrations\->name(\*(Aqfoo\*(Aq);
.Ve
.PP
Name for this set of migrations, defaults to \f(CW\*(C`migrations\*(C'\fR.
.SS "pg"
.IX Subsection "pg"
.Vb 2
\&  my $pg      = $migrations\->pg;
\&  $migrations = $migrations\->pg(Mojo::Pg\->new);
.Ve
.PP
Mojo::Pg object these migrations belong to. Note that this attribute is weakened.
.SH "METHODS"
.IX Header "METHODS"
Mojo::Pg::Migrations inherits all methods from Mojo::Base and implements the following new ones.
.SS "active"
.IX Subsection "active"
.Vb 1
\&  my $version = $migrations\->active;
.Ve
.PP
Currently active version.
.SS "from_data"
.IX Subsection "from_data"
.Vb 3
\&  $migrations = $migrations\->from_data;
\&  $migrations = $migrations\->from_data(\*(Aqmain\*(Aq);
\&  $migrations = $migrations\->from_data(\*(Aqmain\*(Aq, \*(Aqfile_name\*(Aq);
.Ve
.PP
Extract migrations from a file in the \s-1DATA\s0 section of a class with \*(L"data_section\*(R" in Mojo::Loader, defaults to using
the caller class and \*(L"name\*(R".
.PP
.Vb 7
\&  _\|_DATA_\|_
\&  @@ migrations
\&  \-\- 1 up
\&  CREATE TABLE messages (message TEXT);
\&  INSERT INTO messages VALUES (\*(AqI ♥ Mojolicious!\*(Aq);
\&  \-\- 1 down
\&  DROP TABLE messages;
.Ve
.SS "from_dir"
.IX Subsection "from_dir"
.Vb 1
\&  $migrations = $migrations\->from_dir(\*(Aq/home/sri/migrations\*(Aq);
.Ve
.PP
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 \f(CW\*(C`up.sql\*(C'\fR or \f(CW\*(C`down.sql\*(C'\fR.
.PP
.Vb 5
\&  migrations/1/up.sql
\&  migrations/1/down.sql
\&  migrations/2/up.sql
\&  migrations/3/up.sql
\&  migrations/3/down.sql
.Ve
.SS "from_file"
.IX Subsection "from_file"
.Vb 1
\&  $migrations = $migrations\->from_file(\*(Aq/home/sri/migrations.sql\*(Aq);
.Ve
.PP
Extract migrations from a file.
.SS "from_string"
.IX Subsection "from_string"
.Vb 6
\&  $migrations = $migrations\->from_string(
\&    \*(Aq\-\- 1 up
\&     CREATE TABLE foo (bar INT);
\&     \-\- 1 down
\&     DROP TABLE foo;\*(Aq
\&  );
.Ve
.PP
Extract migrations from string.
.SS "latest"
.IX Subsection "latest"
.Vb 1
\&  my $version = $migrations\->latest;
.Ve
.PP
Latest version available.
.SS "migrate"
.IX Subsection "migrate"
.Vb 2
\&  $migrations = $migrations\->migrate;
\&  $migrations = $migrations\->migrate(3);
.Ve
.PP
Migrate from \*(L"active\*(R" to a different version, up or down, defaults to using \*(L"latest\*(R". All version numbers need
to be positive, with version \f(CW0\fR representing an empty database.
.PP
.Vb 2
\&  # Reset database
\&  $migrations\->migrate(0)\->migrate;
.Ve
.SS "sql_for"
.IX Subsection "sql_for"
.Vb 1
\&  my $sql = $migrations\->sql_for(5, 10);
.Ve
.PP
Get \s-1SQL\s0 to migrate from one version to another, up or down.
.SH "DEBUGGING"
.IX Header "DEBUGGING"
You can set the \f(CW\*(C`MOJO_MIGRATIONS_DEBUG\*(C'\fR environment variable to get some advanced diagnostics information printed to
\&\f(CW\*(C`STDERR\*(C'\fR.
.PP
.Vb 1
\&  MOJO_MIGRATIONS_DEBUG=1
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Mojo::Pg, Mojolicious::Guides, <https://mojolicious.org>.