NAME

       Tangram::Relational - 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.