X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FResultSetColumn.pm;h=a459bc3002aca62d38add86c91e4618fac13abfa;hb=94244987e66865e4c0c37385248176330ae69029;hp=35f8fa4574f942a803dbef001f56b717f8e2aecb;hpb=e8419341b29b77a820f5e82ea5a01b6ace750a2e;p=dbsrgits%2FDBIx-Class.git diff --git a/lib/DBIx/Class/ResultSetColumn.pm b/lib/DBIx/Class/ResultSetColumn.pm index 35f8fa4..a459bc3 100644 --- a/lib/DBIx/Class/ResultSetColumn.pm +++ b/lib/DBIx/Class/ResultSetColumn.pm @@ -1,8 +1,16 @@ package DBIx::Class::ResultSetColumn; + use strict; use warnings; + use base 'DBIx::Class'; +use Carp::Clan qw/^DBIx::Class/; +use DBIx::Class::Exception; + +# not importing first() as it will clash with our own method +use List::Util (); + =head1 NAME DBIx::Class::ResultSetColumn - helpful methods for messing @@ -16,7 +24,8 @@ use base 'DBIx::Class'; =head1 DESCRIPTION -A convenience class used to perform operations on a specific column of a resultset. +A convenience class used to perform operations on a specific column of +a resultset. =cut @@ -26,7 +35,8 @@ A convenience class used to perform operations on a specific column of a results my $obj = DBIx::Class::ResultSetColumn->new($rs, $column); -Creates a new resultset column object from the resultset and column passed as params +Creates a new resultset column object from the resultset and column +passed as params. Used internally by L. =cut @@ -34,14 +44,99 @@ sub new { my ($class, $rs, $column) = @_; $class = ref $class if ref $class; - my $object_ref = { _column => $column, - _parent_resultset => $rs }; - - my $new = bless $object_ref, $class; - $new->throw_exception("column must be supplied") unless ($column); + $rs->throw_exception('column must be supplied') unless $column; + + my $orig_attrs = $rs->_resolved_attrs; + my $alias = $rs->current_source_alias; + + # 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 $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 + my %collist = map + { $_ => 1, ($_ =~ /\./) ? () : ( "$alias.$_" => 1 ) } + ($rs->result_source->columns, $column) + ; + if ( + scalar grep + { ! $collist{$_} } + ( $rs->result_source->schema->storage->_extract_order_columns ($orig_attrs->{order_by} ) ) + ) { + # nuke the prefetch before collapsing to sql + my $subq_rs = $rs->search; + $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} && keys %{$orig_attrs->{collapse}}) { + + # scan for a constraint that would contain our column only - that'd be proof + # enough it is unique + my $constraints = { $rs->result_source->unique_constraints }; + for my $constraint_columns ( values %$constraints ) { + + next unless @$constraint_columns == 1; + + my $col = $constraint_columns->[0]; + my $fqcol = join ('.', $new_attrs->{alias}, $col); + + if ($col eq $select or $fqcol eq $select) { + $new_attrs->{group_by} = [ $select ]; + delete $new_attrs->{distinct}; # it is ignored when group_by is present + last; + } + } + + if (!$new_attrs->{group_by}) { + carp ( + "Attempting to retrieve non-unique column '$column' on a resultset containing " + . 'one-to-many joins will return duplicate results.' + ); + } + } + + my $new = bless { _select => $select, _as => $column, _parent_resultset => $new_parent_rs }, $class; return $new; } +=head2 as_query + +=over 4 + +=item Arguments: none + +=item Return Value: \[ $sql, @bind ] + +=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 @@ -52,17 +147,20 @@ sub new { =back -Returns the next value of the column in the resultset (C is there is none). +Returns the next value of the column in the resultset (or C if +there is none). -Much like $rs->next but just returning the one value +Much like L but just returning the +one value. =cut sub next { my $self = shift; - - $self->{_resultset} = $self->{_parent_resultset}->search(undef, {select => [$self->{_column}], as => [$self->{_column}]}) unless ($self->{_resultset}); - my ($row) = $self->{_resultset}->cursor->next; + + # using cursor so we don't inflate anything + my ($row) = $self->_resultset->cursor->next; + return $row; } @@ -76,15 +174,96 @@ sub next { =back -Returns all values of the column in the resultset (C is there are none). +Returns all values of the column in the resultset (or C if +there are none). -Much like $rs->all but returns values rather than row objects +Much like L but returns values rather +than row objects. =cut sub all { my $self = shift; - return map {$_->[0]} $self->{_parent_resultset}->search(undef, {select => [$self->{_column}], as => [$self->{_column}]})->cursor->all; + + # 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. + +=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 if there is none). + +Much like L 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 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 @@ -97,15 +276,35 @@ sub all { =back -Wrapper for ->func. Returns the lowest value of the column in the resultset (C is there are none). + my $first_year = $year_col->min(); + +Wrapper for ->func. Returns the lowest value of the column in the +resultset (or C if there are none). =cut sub min { - my $self = shift; - return $self->func('MIN'); + return shift->func('MIN'); } +=head2 min_rs + +=over 4 + +=item Arguments: none + +=item Return Value: $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 @@ -116,15 +315,35 @@ sub min { =back -Wrapper for ->func. Returns the highest value of the column in the resultset (C is there are none). + my $last_year = $year_col->max(); + +Wrapper for ->func. Returns the highest value of the column in the +resultset (or C if there are none). =cut sub max { - my $self = shift; - return $self->func('MAX'); + return shift->func('MAX'); } +=head2 max_rs + +=over 4 + +=item Arguments: none + +=item Return Value: $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 @@ -135,15 +354,35 @@ sub max { =back -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. + 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 { - my $self = shift; - return $self->func('SUM'); + return shift->func('SUM'); } +=head2 sum_rs + +=over 4 + +=item Arguments: none + +=item Return Value: $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 @@ -154,21 +393,88 @@ sub sum { =back -Runs a query using the function on the column and returns the value. For example $rs = $schema->resultset("CD")->search({}); $length = $rs->get_column('title')->func('LENGTH'); -Produces the following SQL - SELECT LENGTH( title ) from cd me +Runs a query using the function on the column and returns the +value. Produces the following SQL: + + SELECT LENGTH( title ) FROM cd me =cut sub func { + my ($self,$function) = @_; + my $cursor = $self->func_rs($function)->cursor; + + if( wantarray ) { + return map { $_->[ 0 ] } $cursor->all; + } + + return ( $cursor->next )[ 0 ]; +} + +=head2 func_rs + +=over 4 + +=item Arguments: $function + +=item Return Value: $resultset + +=back + +Creates the resultset that C uses to run its query. + +=cut + +sub func_rs { + my ($self,$function) = @_; + return $self->{_parent_resultset}->search( + undef, { + select => {$function => $self->{_select}}, + as => [$self->{_as}], + }, + ); +} + +=head2 throw_exception + +See L 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; - my $function = shift; - my ($row) = $self->{_parent_resultset}->search(undef, {select => {$function => $self->{_column}}, as => [$self->{_column}]})->cursor->next; - return $row; + return $self->{_resultset} ||= $self->{_parent_resultset}->search(undef, + { + select => [$self->{_select}], + as => [$self->{_as}] + } + ); } 1; @@ -177,6 +483,8 @@ sub func { Luke Saunders +Jess Robinson + =head1 LICENSE You may distribute this code under the same terms as Perl itself.