NAME
Rosetta::Schema::View - Describe a single database view or select query
DEPENDENCIES
Perl Version
5.004 (by intent; tested with 5.6)Standard 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.
AUTHOR
Copyright (c) 1999-2003, Darren R. Duncan. All rights reserved. This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. However, I do request that this copyright information and credits remain attached to the file. If you modify this module and redistribute a changed version then please attach a note listing the modifications. This module is available "as-is" and the author can not be held accountable for any problems resulting from its use.
I am always interested in knowing how my work helps others, so if you put this module to use in any of your own products or services then I would appreciate (but not require) it if you send me the website url for said product or service, so I know who you are. Also, if you make non-proprietary changes to the module because it doesn't work the way you need, and you are willing to make these freely available, then please send me a copy so that I can roll desirable changes into the main release.
Address comments, suggestions, and bug reports to perl@DarrenDuncan.net.
SEE ALSO
perl(1), Rosetta::Framework, Rosetta::SimilarModules.