NAME

GraphViz2::DBI - Visualize a database schema as a graph

Synopsis

    use DBI;
    use GraphViz2;
    use GraphViz2::DBI;

    exit 0 if (! $ENV{DBI_DSN});

    my($graph) = GraphViz2->new (
            edge   => {color => 'grey'},
            global => {directed => 1},
            graph  => {rankdir => 'TB'},
            node   => {color => 'blue', shape => 'oval'},
    );
    my($attr)              = {};
    $$attr{sqlite_unicode} = 1 if ($ENV{DBI_DSN} =~ /SQLite/i);
    my($dbh)               = DBI->connect($ENV{DBI_DSN}, $ENV{DBI_USER}, $ENV{DBI_PASS}, $attr);

    $dbh->do('PRAGMA foreign_keys = ON') if ($ENV{DBI_DSN} =~ /SQLite/i);

    my($g) = GraphViz2::DBI->new(dbh => $dbh, graph => $graph);

    $g->create;

    my($format)      = shift || 'svg';
    my($output_file) = shift || File::Spec->catfile('html', "dbi.schema.$format");

    $graph->run(format => $format, output_file => $output_file);

See scripts/dbi.schema.pl ("Scripts Shipped with this Module" in GraphViz2).

The image html/dbi.schema.svg was generated from the database tables of my module App::Office::Contacts.

Description

Takes a database handle, and graphs the schema.

You can write the result in any format supported by Graphviz.

Here is the list of output formats.

Constructor and Initialization

Calling new()

new() is called as my($obj) = GraphViz2::DBI->new(k1 => v1, k2 => v2, ...).

It returns a new object of type GraphViz2::DBI.

Key-value pairs accepted in the parameter list:

• o dbh => $dbh

  This options specifies the database handle to use.

  This key is mandatory.

• o graph => $graphviz_object

  This option specifies the GraphViz2 object to use. This allows you to configure it as desired.

  The default is GraphViz2->new. The default attributes are the same as in the synopsis, above, except for the graph label of course.

  This key is optional.

Methods

create(exclude => [], include => [])

Creates the graph, which is accessible via the graph() method, or via the graph object you passed to new().

Returns $self to allow method chaining.

Parameters:

• o exclude

  An optional arrayref of table names to exclude.

  If none are listed for exclusion, all tables are included.

• o include

  An optional arrayref of table names to include.

  If none are listed for inclusion, all tables are included.

graph()

Returns the graph object, either the one supplied to new() or the one created during the call to new().

FAQ

Why did I get an error about 'Unable to find primary key'?

For plotting foreign keys, the code has an algorithm to find the primary table/key pair which the foreign table/key pair point to.

The steps are listed here, in the order they are tested. The first match stops the search.

• o Ask the database for foreign key information

  DBIx::Admin::TableInfo is used for this.

• o Take a guess

  Assume the foreign key points to a table with a column called id, and use that as the primary key.

• o Die with a detailed error message

Which versions of the servers did you test?

See "FAQ" in DBIx::Admin::TableInfo.

Does GraphViz2::DBI work with SQLite databases?

Yes. See "FAQ" in DBIx::Admin::TableInfo.

What is returned by SQLite's "pragma foreign_key_list($table_name)"?

See "FAQ" in DBIx::Admin::TableInfo.

How does GraphViz2::DBI draw edges from foreign keys to primary keys?

It uses DBIx::Admin::TableInfo.

Scripts Shipped with this Module

scripts/dbi.schema.pl

If the environment vaiables DBI_DSN, DBI_USER and DBI_PASS are set (the latter 2 are optional [e.g. for SQLite]), then this demonstrates building a graph from a database schema.

Also, for Postgres, you can set $ENV{DBI_SCHEMA} to a comma-separated list of schemas, e.g. when processing the MusicBrainz database. See scripts/dbi.schema.pl.

For details, see http://blogs.perl.org/users/ron_savage/2013/03/graphviz2-and-the-dread-musicbrainz-db.html.

Outputs to ./html/dbi.schema.svg by default.

scripts/sqlite.foreign.keys.pl

Demonstrates how to find foreign key info by calling SQLite's pragma foreign_key_list.

Outputs to STDOUT.

Thanks

Many thanks to the people who chose to make Graphviz Open Source.

And thanks to Leon Brocard, who wrote GraphViz, and kindly gave me co-maint of the module.

Author

GraphViz2 was written by Ron Savage ron@savage.net.au in 2011.

Home page: http://savage.net.au/index.html.

Copyright

Australian copyright (c) 2011, Ron Savage.

    All Programs of mine are 'OSI Certified Open Source Software';
    you can redistribute them and/or modify them under the terms of
    The Perl License, a copy of which is available at:
    http://dev.perl.org/licenses/