Tangram::Relational(3) Orthogonal Object Persistence in Relational Databases

SYNOPSIS


use Tangram;
$schema = Tangram::Relational->schema( $hashref );
Tangram::Relational->deploy($schema, $dbh);
$storage = Tangram::Relational->connect( $schema,
$data_source, $username, $password );
$storage->disconnect();
Tangram::Relational->retreat($schema, $dbh);

DESCRIPTION

This is the entry point in the vanilla object-relational persistence backend. Vendor-specific backends should be used when they exist. Currently Mysql, Sybase and Oracle have such backends; see Tangram::mysql, Tangram::Sybase and Tangram::Oracle.

More backends could be added in the future; they might implement persistence in XML documents, pure object databases, using C database libraries to bypass the need for an RDBMS, etc.

CLASS METHODS

schema

   $schema = Tangram::Relational->schema( $hashref );

Returns a new Schema object. See Tangram::Schema.

deploy

   Tangram::Relational->deploy($schema);
   Tangram::Relational->deploy($schema, HANDLE);
   Tangram::Relational->deploy($schema, @dbi_args);

Writes SQL statements for preparing a database for use with the given $schema.

Called with a single argument, writes SQL statements to STDOUT.

Called with two arguments, writes SQL statements to HANDLE. HANDLE may be a DBI connection handle or a file handle.

Called with more than two arguments, passes all but the first to DBI::connect() and writes statements to the resulting DBI handle, which is automatically closed.

The SQL code is only guaranteed to work on newly created databases.

connect

   $storage = Tangram::Relational->connect( $schema,
      $data_source, $user, $password, \%options )

Connects to a storage and return a handle object. Dies in case of failure.

$schema is a Schema object describing the system of classes stored in the database.

$data_source, $user and $password are passed directly to DBI::connect().

\%options is a reference to a hash containing connection options. See Tangram::Storage for a description of available options.

retreat

   Tangram::Relational->retreat($schema);
   Tangram::Relational->retreat($schema, HANDLE);
   Tangram::Relational->retreat($schema, @dbi_args);

Remove the tables created by deploy(). Only guaranteed to work against a database that was deployed using exactly the same schema.

For an explanation of the possible argument lists, see deploy.

WRITING A VENDOR DRIVER

Like Charles Moore (inventor of Forth) used to say, ``standards are great, everybody should have one!''.

Tangram can take advantage of extensions available in some SQL dialects.

To create a vendor-specific driver, call it "Tangram::Foo" (where "Foo" is the name of the DBI driver, as would be selected with the DBI connection string "dbi:Foo:"), and derive "Tangram::Relational".

For now, the existing back-ends should be used as examples of how to extend Tangram to support different databases or utilise some of their more exotic features.

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