dbix::class::helper::resultset::virtualview(3pm) [debian man page]

DBIx::Class::Helper::ResultSet::VirtualView(3pm)	User Contributed Perl Documentation	  DBIx::Class::Helper::ResultSet::VirtualView(3pm)

NAME

       DBIx::Class::Helper::ResultSet::VirtualView - Clean up your SQL namespace (DEPRECATED)

VERSION

       version 2.013002

SYNOPSIS

	# note that this is normally a component for a ResultSet
	package MySchema::ResultSet::Bar;

	use strict;
	use warnings;

	use parent 'DBIx::Class::ResultSet';

	__PACKAGE__->load_components('Helper::ResultSet::VirtualView');

	# and then in code that uses the ResultSet Join with relation x
	my $rs = $schema->resultset('Bar')->search({'x.name' => 'abc'},{ join => 'x' });

	# 'x' now pollutes the query namespace

	# So the following works as expected
	my $ok_rs = $rs->search({'x.other' => 1});

	# But this doesn't: instead of finding a 'Bar' related to two x rows (abc and
	# def) we look for one row with contradictory terms and join in another table
	# (aliased 'x_2') which we never use
	my $broken_rs = $rs->search({'x.name' => 'def'});

	my $rs2 = $rs->as_virtual_view;

	# doesn't work - 'x' is no longer accessible in $rs2, having been sealed away
	my $not_joined_rs = $rs2->search({'x.other' => 1});

	# works as expected: finds a 'table' row related to two x rows (abc and def)
	my $correctly_joined_rs = $rs2->search({'x.name' => 'def'});

DESCRIPTION

       This component is will allow you to clean up your SQL namespace.  See "NOTE" in DBIx::Class::Helper::ResultSet for a nice way to apply it
       to your entire schema.

DEPRECATED

       This component has been suplanted by DBIx::Class::ResultSet::as_subselect_rs.  In the next major version(3) we will begin issuing a
       warning on it's use.  In the major version after that(4) we will remove it entirely.

METHODS

   as_virtual_view
       Act as a barrier to SQL symbols.  The resultset provided will be made into a "virtual view" by including it as a subquery within the from
       clause.	From this point on, any joined tables are inaccessible to ->search on the resultset (as if it were simply where-filtered without
       joins).	See "SYNOPSIS" for example.

NOTE

       You don't have to use this as a Component.  If you prefer you can use it in the following manner:

	# in code using ResultSet:
	use DBIx::Class:Helper::VirtualView;

	my $new_rs = DBIx::Class::Helper::VirtualView::as_virtual_view($rs);

THANKS

       Thanks to ijw from #dbix-class for the idea for this helper (originally called seal), most of the code, and most of the documentation.

AUTHOR

       Arthur Axel "fREW" Schmidt <frioux+cpan@gmail.com>

COPYRIGHT AND LICENSE

       This software is copyright (c) 2012 by Arthur Axel "fREW" Schmidt.

       This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

perl v5.14.2							    2012-06-18			  DBIx::Class::Helper::ResultSet::VirtualView(3pm)

DBIx::Class::Helper::ResultSet::CorrelateRelationship(3pUser Contributed Perl DocumentatDBIx::Class::Helper::ResultSet::CorrelateRelationship(3pm)

NAME

       DBIx::Class::Helper::ResultSet::CorrelateRelationship - Easily correlate your ResultSets

VERSION

       version 2.013002

SYNOPSIS

	package MyApp::Schema::ResultSet::Author;

	use base 'DBIx::Class::ResultSet';

	__PACKAGE__->load_components(qw(Helper::ResultSet::CorrelateRelationship));

	sub with_book_count {
	  my $self = shift;

	  $self->search(undef, {
	    '+columns' => {
	      book_count => $self->correlate('book')->count_rs->as_query
	    }
	  });
	}

	1;

       And then elsewhere, like in a controller:

	my $rows = $schema->resultset('Author')->with_book_count->all;

DESCRIPTION

       Correlated queries are one of the coolest things I've learned about for SQL since my initial learning of SQL.  Unfortunately they are
       somewhat confusing.  DBIx::Class has supported doing them for a long time, but generally people don't think of them because they are so
       rare.  I won't go through all the details of how they work and cool things you can do with them, but here are a couple high level things
       you can use them for to save you time or effort.

       If you want to select a list of authors and counts of books for each author, you could use "group_by" and something like "COUNT(book.id)",
       but then you'd need to make your select list match your "group_by" and it would just be a hassle forever after that.  The "SYNOPSIS" is a
       perfect example of how to implement this.

       If you want to select a list of authors and two separate kinds of counts of books for each author, as far as I know, you must use a
       correlated subquery in DBIx::Class.  Here is an example of how you might do that:

	package MyApp::Schema::ResultSet::Author;

	use base 'DBIx::Class::ResultSet';

	__PACKAGE__->load_components(qw(Helper::ResultSet::CorrelateRelationship));

	sub with_good_book_count {
	  my $self = shift;

	  $self->search(undef, {
	    '+columns' => {
	      good_book_count => $self->correlate('books')->good->count_rs->as_query
	    }
	  });
	}

	sub with_bad_book_count {
	  my $self = shift;

	  $self->search(undef, {
	    '+columns' => {
	      bad_book_count => $self->correlate('books')->bad->count_rs->as_query
	    }
	  });
	}

	1;

       And then elsewhere, like in a controller:

	my $rows = $schema->resultset('Author')
	  ->with_bad_book_count
	  ->with_good_book_count
	  ->all;

       This assumes that the Book resultset has "good" and "bad" methods.

       See "NOTE" in DBIx::Class::Helper::ResultSet for a nice way to apply it to your entire schema.

METHODS

   correlate
	$rs->correlate($relationship_name)

       Correlate takes a single argument, a relationship for the invocant, and returns a resultset that can be used in the selector list.

AUTHOR

       Arthur Axel "fREW" Schmidt <frioux+cpan@gmail.com>

COPYRIGHT AND LICENSE

       This software is copyright (c) 2012 by Arthur Axel "fREW" Schmidt.

       This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

perl v5.14.2							    2012-06-18		DBIx::Class::Helper::ResultSet::CorrelateRelationship(3pm)