NAME
Rosetta::Schema::View - Describe a single database view or select query
ABSTRACT
See the file Rosetta::Framework for the main Rosetta documentation.
COPYRIGHT AND LICENSE
This file is part of the Rosetta database abstraction framework.
Rosetta is Copyright (c) 1999-2003, Darren R. Duncan. All rights reserved. Address comments, suggestions, and bug reports to perl@DarrenDuncan.net, or visit "http://www.DarrenDuncan.net" for more information.
Rosetta is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License (GPL) version 2 as published by the Free Software Foundation (http://www.fsf.org/). You should have received a copy of the GPL as part of the Rosetta distribution, in the file named "LICENSE"; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
Any versions of Rosetta that you modify and distribute must carry prominent notices stating that you changed the files and the date of any changes, in addition to preserving this original copyright notice and other credits. Rosetta is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GPL for more details.
Linking Rosetta statically or dynamically with other modules is making a combined work based on Rosetta. Thus, the terms and conditions of the GPL cover the whole combination.
As a special exception, the copyright holders of Rosetta give you permission to link Rosetta with independent modules that communicate with Rosetta solely through the "Driver" interface (because they are interfaces to or implementations of databases), regardless of the license terms of these independent modules, and to copy and distribute the resulting combined work under terms of your choice, provided that every copy of the combined work is accompanied by a complete copy of the source code of Rosetta (the version of Rosetta used to produce the combined work), being distributed under the terms of the GPL plus this exception. An independent module is a module which is not derived from or based on Rosetta, and which is fully useable when not linked to Rosetta in any form.
Note that people who make modified versions of Rosetta are not obligated to grant this special exception for their modified versions; it is their choice whether to do so. The GPL gives permission to release a modified version without this exception; this exception also makes it possible to release a modified version which carries forward this exception.
While it is by no means required, the copyright holders of Rosetta would appreciate being informed any time you create a modified version of Rosetta that you are willing to distribute, because that is a practical way of suggesting improvements to the standard version.
DEPENDENCIES
Perl Version
5.004Standard Modules
I<none>Nonstandard Modules
Rosetta::Schema::DataType
Rosetta::Schema::TableSYNOPSIS
my %view_info = map {
( $_->{name}, Rosetta::Schema::View->new( $_ ) )
} (
{
'name' => 'user',
'source_list' => [
{ 'name' => 'user_auth', 'source' => $table_info{user_auth}, },
{ 'name' => 'user_profile', 'source' => $table_info{user_profile}, },
],
'column_list' => [
{ 'name' => 'user_id' , 'source' => 'user_auth' , },
{ 'name' => 'login_name' , 'source' => 'user_auth' , },
{ 'name' => 'login_pass' , 'source' => 'user_auth' , },
{ 'name' => 'private_name' , 'source' => 'user_auth' , },
{ 'name' => 'private_email', 'source' => 'user_auth' , },
{ 'name' => 'may_login' , 'source' => 'user_auth' , },
{ 'name' => 'max_sessions' , 'source' => 'user_auth' , },
{ 'name' => 'public_name' , 'source' => 'user_profile', },
{ 'name' => 'public_email' , 'source' => 'user_profile', },
{ 'name' => 'web_url' , 'source' => 'user_profile', },
{ 'name' => 'contact_net' , 'source' => 'user_profile', },
{ 'name' => 'contact_phy' , 'source' => 'user_profile', },
{ 'name' => 'bio' , 'source' => 'user_profile', },
{ 'name' => 'plan' , 'source' => 'user_profile', },
{ 'name' => 'comments' , 'source' => 'user_profile', },
],
'join_list' => [
{
'lhs_source' => 'user_auth',
'rhs_source' => 'user_profile',
'join_type' => 'left',
'column_list' => [
{ 'lhs_column' => 'user_id', 'rhs_column' => 'user_id', },
],
},
],
},
{
'name' => 'person_with_parents',
'source_list' => [
{ 'name' => 'self', 'source' => $table_info{person}, },
{ 'name' => 'father', 'source' => $table_info{person}, },
{ 'name' => 'mother', 'source' => $table_info{person}, },
],
'column_list' => [
{ 'name' => 'self_id' , 'source' => 'self' , 'column' => 'person_id', },
{ 'name' => 'self_name' , 'source' => 'self' , 'column' => 'name' , },
{ 'name' => 'father_id' , 'source' => 'father', 'column' => 'person_id', },
{ 'name' => 'father_name', 'source' => 'father', 'column' => 'name' , },
{ 'name' => 'mother_id' , 'source' => 'mother', 'column' => 'person_id', },
{ 'name' => 'mother_name', 'source' => 'mother', 'column' => 'name' , },
],
'join_list => [
{
'lhs_source' => 'self',
'rhs_source' => 'father',
'join_type' => 'left',
'column_list' => [
{ 'lhs_column' => 'person_id', 'rhs_column' => 'person_id', },
],
},
{
'lhs_source' => 'self',
'rhs_source' => 'mother',
'join_type' => 'left',
'column_list' => [
{ 'lhs_column' => 'person_id', 'rhs_column' => 'person_id', },
],
},
],
},
);DESCRIPTION
This Perl 5 object class is a core component of the Rosetta framework, and is part of the "Rosetta Native Interface" (RNI). It is a "Schema" class, meaning its objects are pure containers that can be serialized or stored indefinately off site for later retrieval and use, such as in a data dictionary.
Each Rosetta::Schema::View object describes a single database view, which conceptually looks like a table, but it is used differently. Tables and views are similar in that they both represent or store a matrix of data, which has uniquely identifiable columns, and rows which can be uniquely identifiable but may not be. With the way that Rosetta implements views, you can do all of the same DML operations with them that you can do with tables: select, insert, update, delete rows; that said, the process for doing any of those with views is more complicated than with tables, but this complexity is usually internal to Rosetta so you shouldn't have to code any differently between them. Tables and views are different in that tables actually store data in themselves, while views don't. A view is actually a custom abstracted interface to one or more database tables which are related to each other in a specific way; when you issue DML against a view, you are actually fetching from or modifying the data stored in one (simplest case) or more tables.
Views are also conceptually just select queries (and with some RDBMS systems, that is exactly how they are stored), but Rosetta::Schema::View objects have enough meta-data so that if a program wants to, for example, modify a row selected through one, Rosetta could calculate which composite table rows to update (views built in to RDBMS systems are typically read-only by contrast). Given that Rosetta views are used mainly just for DML, they do not need to be stored in a database like a table, and so they do not need to have names like tables do. However, if you want to store a view in the database like an RDBMS native view, for added select performance, this class will let you associate a name with one.
This class does not describe anything that is changed by DML activity, such as a count of stored records. This class can be used both when manipulating database schema (stored RDBMS native views) and when manipulating database data (normal use).
This class can generate Rosetta::Engine::Command objects having types of: 'data_select', 'data_insert', 'data_update', 'data_delete', 'data_lock', 'data_unlock', 'view_verify', 'view_create', 'view_alter', 'view_destroy'.
CLASS PROPERTIES
These are the conceptual properties of a Rosetta::Schema::View object:
SYNTAX
This class does not export any functions or methods, so you need to call them using object notation. This means using Class->function() for functions and $object->method() for methods. If you are inheriting this class for your own modules, then that often means something like $self->method().
FUNCTIONS AND METHODS
Note: this class is incomplete, and so most of its methods are missing.
new([ INITIALIZER ])
This function creates a new Rosetta::Schema::View (or subclass) object and returns it. All of the method arguments are passed to initialize() as is; please see the POD for that method for an explanation of them.
initialize([ INITIALIZER ])
This method is used by new() to set the initial properties of objects that it creates. Nothing is returned.
clone([ CLONE ])
This method initializes a new object to have all of the same properties of the current object and returns it. This new object can be provided in the optional argument CLONE (if CLONE is an object of the same class as the current object); otherwise, a brand new object of the current class is used. Only object properties recognized by Rosetta::Schema::View are set in the clone; other properties are not changed.
SEE ALSO
perl(1), Rosetta::Framework, Rosetta::SimilarModules.