—————————————————package
DBIx::Class::ResultSetColumn;
use
strict;
use
warnings;
use
DBIx::Class::Carp;
use
namespace::clean;
# not importing first() as it will clash with our own method
use
List::Util ();
=head1 NAME
DBIx::Class::ResultSetColumn - helpful methods for messing
with a single column of the resultset
=head1 SYNOPSIS
$rs = $schema->resultset('CD')->search({ artist => 'Tool' });
$rs_column = $rs->get_column('year');
$max_year = $rs_column->max; #returns latest year
=head1 DESCRIPTION
A convenience class used to perform operations on a specific column of
a resultset.
=cut
=head1 METHODS
=head2 new
my $obj = DBIx::Class::ResultSetColumn->new($rs, $column);
Creates a new resultset column object from the resultset and column
passed as params. Used internally by L<DBIx::Class::ResultSet/get_column>.
=cut
sub
new {
my
(
$class
,
$rs
,
$column
) =
@_
;
$class
=
ref
$class
if
ref
$class
;
$rs
->throw_exception(
'column must be supplied'
)
unless
$column
;
my
$orig_attrs
=
$rs
->_resolved_attrs;
my
$alias
=
$rs
->current_source_alias;
my
$rsrc
=
$rs
->result_source;
# If $column can be found in the 'as' list of the parent resultset, use the
# corresponding element of its 'select' list (to keep any custom column
# definition set up with 'select' or '+select' attrs), otherwise use $column
# (to create a new column definition on-the-fly).
my
$as_list
=
$orig_attrs
->{as} || [];
my
$select_list
=
$orig_attrs
->{
select
} || [];
my
$as_index
= List::Util::first { (
$as_list
->[
$_
] ||
""
) eq
$column
} 0..
$#$as_list
;
my
$select
=
defined
$as_index
?
$select_list
->[
$as_index
] :
$column
;
my
$colmap
;
for
(
$rsrc
->columns,
$column
) {
if
(
$_
=~ /^ \Q
$alias
\E \. ([^\.]+) $ /x) {
$colmap
->{
$_
} = $1;
}
elsif
(
$_
!~ /\./) {
$colmap
->{
"$alias.$_"
} =
$_
;
$colmap
->{
$_
} =
$_
;
}
}
my
$new_parent_rs
;
# analyze the order_by, and see if it is done over a function/nonexistentcolumn
# if this is the case we will need to wrap a subquery since the result of RSC
# *must* be a single column select
if
(
scalar
grep
{ !
exists
$colmap
->{
$_
->[0]} }
(
$rsrc
->schema->storage->_extract_order_criteria (
$orig_attrs
->{order_by} ) )
) {
# nuke the prefetch before collapsing to sql
my
$subq_rs
=
$rs
->search_rs;
$subq_rs
->{attrs}{
join
} =
$subq_rs
->_merge_joinpref_attr(
$subq_rs
->{attrs}{
join
},
delete
$subq_rs
->{attrs}{prefetch} );
$new_parent_rs
=
$subq_rs
->as_subselect_rs;
}
$new_parent_rs
||=
$rs
->search_rs;
my
$new_attrs
=
$new_parent_rs
->{attrs} ||= {};
# prefetch causes additional columns to be fetched, but we can not just make a new
# rs via the _resolved_attrs trick - we need to retain the separation between
# +select/+as and select/as. At the same time we want to preserve any joins that the
# prefetch would otherwise generate.
$new_attrs
->{
join
} =
$rs
->_merge_joinpref_attr(
$new_attrs
->{
join
},
delete
$new_attrs
->{prefetch} );
# {collapse} would mean a has_many join was injected, which in turn means
# we need to group *IF WE CAN* (only if the column in question is unique)
if
(!
$orig_attrs
->{group_by} &&
$orig_attrs
->{collapse}) {
if
(
$colmap
->{
$select
} and
$rsrc
->_identifying_column_set([
$colmap
->{
$select
}])) {
$new_attrs
->{group_by} = [
$select
];
delete
@{
$new_attrs
}{
qw(distinct _grouped_by_distinct)
};
# it is ignored when group_by is present
}
else
{
carp (
"Attempting to retrieve non-unique column '$column' on a resultset containing "
.
'one-to-many joins will return duplicate results.'
);
}
}
return
bless
{
_select
=>
$select
,
_as
=>
$column
,
_parent_resultset
=>
$new_parent_rs
},
$class
;
}
=head2 as_query
=over 4
=item Arguments: none
=item Return Value: \[ $sql, L<@bind_values|DBIx::Class::ResultSet/DBIC BIND VALUES> ]
=back
Returns the SQL query and bind vars associated with the invocant.
This is generally used as the RHS for a subquery.
=cut
sub
as_query {
return
shift
->_resultset->as_query(
@_
) }
=head2 next
=over 4
=item Arguments: none
=item Return Value: $value
=back
Returns the next value of the column in the resultset (or C<undef> if
there is none).
Much like L<DBIx::Class::ResultSet/next> but just returning the
one value.
=cut
sub
next
{
my
$self
=
shift
;
# using cursor so we don't inflate anything
my
(
$row
) =
$self
->_resultset->cursor->
next
;
return
$row
;
}
=head2 all
=over 4
=item Arguments: none
=item Return Value: @values
=back
Returns all values of the column in the resultset (or C<undef> if
there are none).
Much like L<DBIx::Class::ResultSet/all> but returns values rather
than result objects.
=cut
sub
all {
my
$self
=
shift
;
# using cursor so we don't inflate anything
return
map
{
$_
->[0] }
$self
->_resultset->cursor->all;
}
=head2 reset
=over 4
=item Arguments: none
=item Return Value: $self
=back
Resets the underlying resultset's cursor, so you can iterate through the
elements of the column again.
Much like L<DBIx::Class::ResultSet/reset>.
=cut
sub
reset
{
my
$self
=
shift
;
$self
->_resultset->cursor->
reset
;
return
$self
;
}
=head2 first
=over 4
=item Arguments: none
=item Return Value: $value
=back
Resets the underlying resultset and returns the next value of the column in the
resultset (or C<undef> if there is none).
Much like L<DBIx::Class::ResultSet/first> but just returning the one value.
=cut
sub
first {
my
$self
=
shift
;
# using cursor so we don't inflate anything
$self
->_resultset->cursor->
reset
;
my
(
$row
) =
$self
->_resultset->cursor->
next
;
return
$row
;
}
=head2 single
=over 4
=item Arguments: none
=item Return Value: $value
=back
Much like L<DBIx::Class::ResultSet/single> fetches one and only one column
value using the cursor directly. If additional rows are present a warning
is issued before discarding the cursor.
=cut
sub
single {
my
$self
=
shift
;
my
$attrs
=
$self
->_resultset->_resolved_attrs;
my
(
$row
) =
$self
->_resultset->result_source->storage->select_single(
$attrs
->{from},
$attrs
->{
select
},
$attrs
->{where},
$attrs
);
return
$row
;
}
=head2 min
=over 4
=item Arguments: none
=item Return Value: $lowest_value
=back
my $first_year = $year_col->min();
Wrapper for ->func. Returns the lowest value of the column in the
resultset (or C<undef> if there are none).
=cut
sub
min {
return
shift
->func(
'MIN'
);
}
=head2 min_rs
=over 4
=item Arguments: none
=item Return Value: L<$resultset|DBIx::Class::ResultSet>
=back
my $rs = $year_col->min_rs();
Wrapper for ->func_rs for function MIN().
=cut
sub
min_rs {
return
shift
->func_rs(
'MIN'
) }
=head2 max
=over 4
=item Arguments: none
=item Return Value: $highest_value
=back
my $last_year = $year_col->max();
Wrapper for ->func. Returns the highest value of the column in the
resultset (or C<undef> if there are none).
=cut
sub
max {
return
shift
->func(
'MAX'
);
}
=head2 max_rs
=over 4
=item Arguments: none
=item Return Value: L<$resultset|DBIx::Class::ResultSet>
=back
my $rs = $year_col->max_rs();
Wrapper for ->func_rs for function MAX().
=cut
sub
max_rs {
return
shift
->func_rs(
'MAX'
) }
=head2 sum
=over 4
=item Arguments: none
=item Return Value: $sum_of_values
=back
my $total = $prices_col->sum();
Wrapper for ->func. Returns the sum of all the values in the column of
the resultset. Use on varchar-like columns at your own risk.
=cut
sub
sum {
return
shift
->func(
'SUM'
);
}
=head2 sum_rs
=over 4
=item Arguments: none
=item Return Value: L<$resultset|DBIx::Class::ResultSet>
=back
my $rs = $year_col->sum_rs();
Wrapper for ->func_rs for function SUM().
=cut
sub
sum_rs {
return
shift
->func_rs(
'SUM'
) }
=head2 func
=over 4
=item Arguments: $function
=item Return Value: $function_return_value
=back
$rs = $schema->resultset("CD")->search({});
$length = $rs->get_column('title')->func('LENGTH');
Runs a query using the function on the column and returns the
value. Produces the following SQL:
SELECT LENGTH( title ) FROM cd me
=cut
sub
func {
my
(
$self
,
$function
) =
@_
;
my
$cursor
=
$self
->func_rs(
$function
)->cursor;
if
(
wantarray
) {
DBIx::Class::_ENV_::ASSERT_NO_INTERNAL_WANTARRAY and
my
$sog
= fail_on_internal_wantarray(
$self
);
return
map
{
$_
->[ 0 ] }
$cursor
->all;
}
return
(
$cursor
->
next
)[ 0 ];
}
=head2 func_rs
=over 4
=item Arguments: $function
=item Return Value: L<$resultset|DBIx::Class::ResultSet>
=back
Creates the resultset that C<func()> uses to run its query.
=cut
sub
func_rs {
my
(
$self
,
$function
) =
@_
;
my
$rs
=
$self
->{_parent_resultset};
my
$select
=
$self
->{_select};
# wrap a grouped rs
if
(
$rs
->_resolved_attrs->{group_by}) {
$select
=
$self
->{_as};
$rs
=
$rs
->as_subselect_rs;
}
$rs
->search(
undef
, {
columns
=> {
$self
->{_as} => {
$function
=>
$select
} }
} );
}
=head2 throw_exception
See L<DBIx::Class::Schema/throw_exception> for details.
=cut
sub
throw_exception {
my
$self
=
shift
;
if
(
ref
$self
&&
$self
->{_parent_resultset}) {
$self
->{_parent_resultset}->throw_exception(
@_
);
}
else
{
DBIx::Class::Exception->throw(
@_
);
}
}
# _resultset
#
# Arguments: none
#
# Return Value: $resultset
#
# $year_col->_resultset->next
#
# Returns the underlying resultset. Creates it from the parent resultset if
# necessary.
#
sub
_resultset {
my
$self
=
shift
;
return
$self
->{_resultset} ||=
do
{
my
$select
=
$self
->{_select};
if
(
$self
->{_parent_resultset}{attrs}{distinct}) {
my
$alias
=
$self
->{_parent_resultset}->current_source_alias;
my
$rsrc
=
$self
->{_parent_resultset}->result_source;
my
%cols
=
map
{
$_
=> 1,
"$alias.$_"
=> 1 }
$rsrc
->columns;
unless
(
$cols
{
$select
} ) {
carp_unique(
'Use of distinct => 1 while selecting anything other than a column '
.
'declared on the primary ResultSource is deprecated - please supply '
.
'an explicit group_by instead'
);
# collapse the selector to a literal so that it survives the distinct parse
# if it turns out to be an aggregate - at least the user will get a proper exception
# instead of silent drop of the group_by altogether
$select
= \
$rsrc
->storage->sql_maker->_recurse_fields(
$select
);
}
}
$self
->{_parent_resultset}->search(
undef
, {
columns
=> {
$self
->{_as} =>
$select
}
});
};
}
1;
=head1 AUTHOR AND CONTRIBUTORS
See L<AUTHOR|DBIx::Class/AUTHOR> and L<CONTRIBUTORS|DBIx::Class/CONTRIBUTORS> in DBIx::Class
=head1 LICENSE
You may distribute this code under the same terms as Perl itself.
=cut