# NAME

[GraphViz2::DBI](https://metacpan.org/pod/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](https://metacpan.org/pod/GraphViz2#Scripts-Shipped-with-this-Module)).

The image html/dbi.schema.svg was generated from the database tables of my module
[App::Office::Contacts](https://metacpan.org/pod/App::Office::Contacts).

# Description

Takes a database handle, and graphs the schema.

You can write the result in any format supported by [Graphviz](http://www.graphviz.org/).

Here is the list of [output formats](http://www.graphviz.org/content/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](https://metacpan.org/pod/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](https://metacpan.org/pod/DBIx::Admin::TableInfo#FAQ).

## Does GraphViz2::DBI work with SQLite databases?

Yes. See ["FAQ" in DBIx::Admin::TableInfo](https://metacpan.org/pod/DBIx::Admin::TableInfo#FAQ).

## What is returned by SQLite's "pragma foreign\_key\_list($table\_name)"?

See ["FAQ" in DBIx::Admin::TableInfo](https://metacpan.org/pod/DBIx::Admin::TableInfo#FAQ).

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

It uses [DBIx::Admin::TableInfo](https://metacpan.org/pod/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](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](http://www.graphviz.org/) Open Source.

And thanks to [Leon Brocard](http://search.cpan.org/~lbrocard/), who wrote [GraphViz](https://metacpan.org/pod/GraphViz), and kindly
gave me co-maint of the module.

# Author

[GraphViz2](https://metacpan.org/pod/GraphViz2) was written by Ron Savage _<[email protected]>_ in 2011.

Home page: [http://savage.net.au/index.html](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/

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