X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=dbsrgits%2FDBIx-Class.git;a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FResultSet.pm;h=c6935c35c2a9866577a092bf3b9a956f142e87cd;hp=b5397b6abd50b891f87325a94b2e102e5983bd9e;hb=d71502b;hpb=9ae300a43ff4db9bf5084a009cce726c694f3612 diff --git a/lib/DBIx/Class/ResultSet.pm b/lib/DBIx/Class/ResultSet.pm index b5397b6..c6935c3 100644 --- a/lib/DBIx/Class/ResultSet.pm +++ b/lib/DBIx/Class/ResultSet.pm @@ -5,7 +5,7 @@ use warnings; use base qw/DBIx::Class/; use DBIx::Class::Carp; use DBIx::Class::ResultSetColumn; -use Scalar::Util qw/blessed weaken/; +use Scalar::Util qw/blessed weaken reftype/; use Try::Tiny; use Data::Compare (); # no imports!!! guard against insane architecture @@ -25,6 +25,10 @@ use overload 'bool' => "_bool", fallback => 1; +# this is real - CDBICompat overrides it with insanity +# yes, prototype won't matter, but that's for now ;) +sub _bool () { 1 } + __PACKAGE__->mk_group_accessors('simple' => qw/_result_class result_source/); =head1 NAME @@ -137,11 +141,15 @@ another. =head3 Resolving conditions and attributes -When a resultset is chained from another resultset, conditions and -attributes with the same keys need resolving. +When a resultset is chained from another resultset (ie: +Csearch(\%extra_cond, \%attrs)>), conditions +and attributes with the same keys need resolving. + +If any of L, L, L are present, they reset the +original selection, and start the selection "clean". -L, L, L, L attributes are merged -into the existing ones from the original resultset. +The L, L, L, L, L attributes +are merged into the existing ones from the original resultset. The L and L attributes, and any search conditions, are merged with an SQL C to the existing condition from the original @@ -236,7 +244,9 @@ sub new { my ($source, $attrs) = @_; $source = $source->resolve if $source->isa('DBIx::Class::ResultSourceHandle'); + $attrs = { %{$attrs||{}} }; + delete @{$attrs}{qw(_sqlmaker_select_args _related_results_construction)}; if ($attrs->{page}) { $attrs->{rows} ||= 10; @@ -295,7 +305,7 @@ call it as C. For a list of attributes that can be passed to C, see L. For more examples of using this function, see L. For a complete -documentation for the first argument, see L +documentation for the first argument, see L and its extension L. For more help on using joins with search, see L. @@ -399,8 +409,7 @@ sub search_rs { } my $old_attrs = { %{$self->{attrs}} }; - my $old_having = delete $old_attrs->{having}; - my $old_where = delete $old_attrs->{where}; + my ($old_having, $old_where) = delete @{$old_attrs}{qw(having where)}; my $new_attrs = { %$old_attrs }; @@ -435,6 +444,7 @@ sub search_rs { # older deprecated name, use only if {columns} is not there if (my $c = delete $new_attrs->{cols}) { + carp_unique( "Resultset attribute 'cols' is deprecated, use 'columns' instead" ); if ($new_attrs->{columns}) { carp "Resultset specifies both the 'columns' and the legacy 'cols' attributes - ignoring 'cols'"; } @@ -481,8 +491,12 @@ sub _normalize_selection { my ($self, $attrs) = @_; # legacy syntax - $attrs->{'+columns'} = $self->_merge_attr($attrs->{'+columns'}, delete $attrs->{include_columns}) - if exists $attrs->{include_columns}; + if ( exists $attrs->{include_columns} ) { + carp_unique( "Resultset attribute 'include_columns' is deprecated, use '+columns' instead" ); + $attrs->{'+columns'} = $self->_merge_attr( + $attrs->{'+columns'}, delete $attrs->{include_columns} + ); + } # columns are always placed first, however @@ -838,7 +852,7 @@ sub find { # Run the query, passing the result_class since it should propagate for find my $rs = $self->search ($final_cond, {result_class => $self->result_class, %$attrs}); - if (keys %{$rs->_resolved_attrs->{collapse}}) { + if ($rs->_resolved_attrs->{collapse}) { my $row = $rs->next; carp "Query returned more than one row" if $rs->next; return $row; @@ -990,7 +1004,7 @@ sub cursor { my $self = shift; return $self->{cursor} ||= do { - my $attrs = { %{$self->_resolved_attrs } }; + my $attrs = $self->_resolved_attrs; $self->result_source->storage->select( $attrs->{from}, $attrs->{select}, $attrs->{where}, $attrs ); @@ -1048,11 +1062,9 @@ sub single { my $attrs = { %{$self->_resolved_attrs} }; - if (keys %{$attrs->{collapse}}) { - $self->throw_exception( - 'single() can not be used on resultsets prefetching has_many. Use find( \%cond ) or next() instead' - ); - } + $self->throw_exception( + 'single() can not be used on resultsets collapsing a has_many. Use find( \%cond ) or next() instead' + ) if $attrs->{collapse}; if ($where) { if (defined $attrs->{where}) { @@ -1066,12 +1078,14 @@ sub single { } } - my @data = $self->result_source->storage->select_single( + my $data = [ $self->result_source->storage->select_single( $attrs->{from}, $attrs->{select}, $attrs->{where}, $attrs - ); + )]; - return (@data ? ($self->_construct_object(@data))[0] : undef); + return undef unless @$data; + $self->{_stashed_rows} = [ $data ]; + $self->_construct_results->[0]; } @@ -1228,161 +1242,283 @@ first record from the resultset. sub next { my ($self) = @_; + if (my $cache = $self->get_cache) { $self->{all_cache_position} ||= 0; return $cache->[$self->{all_cache_position}++]; } + if ($self->{attrs}{cache}) { delete $self->{pager}; $self->{all_cache_position} = 1; return ($self->all)[0]; } - if ($self->{stashed_objects}) { - my $obj = shift(@{$self->{stashed_objects}}); - delete $self->{stashed_objects} unless @{$self->{stashed_objects}}; - return $obj; - } - my @row = ( - exists $self->{stashed_row} - ? @{delete $self->{stashed_row}} - : $self->cursor->next - ); - return undef unless (@row); - my ($row, @more) = $self->_construct_object(@row); - $self->{stashed_objects} = \@more if @more; - return $row; -} -sub _construct_object { - my ($self, @row) = @_; + return shift(@{$self->{_stashed_results}}) if @{ $self->{_stashed_results}||[] }; - my $info = $self->_collapse_result($self->{_attrs}{as}, \@row) - or return (); - my @new = $self->result_class->inflate_result($self->result_source, @$info); - @new = $self->{_attrs}{record_filter}->(@new) - if exists $self->{_attrs}{record_filter}; - return @new; -} + $self->{_stashed_results} = $self->_construct_results + or return undef; -sub _collapse_result { - my ($self, $as_proto, $row) = @_; + return shift @{$self->{_stashed_results}}; +} - my @copy = @$row; +# Constructs as many results as it can in one pass while respecting +# cursor laziness. Several modes of operation: +# +# * Always builds everything present in @{$self->{_stashed_rows}} +# * If called with $fetch_all true - pulls everything off the cursor and +# builds all result structures (or objects) in one pass +# * If $self->_resolved_attrs->{collapse} is true, checks the order_by +# and if the resultset is ordered properly by the left side: +# * Fetches stuff off the cursor until the "master object" changes, +# and saves the last extra row (if any) in @{$self->{_stashed_rows}} +# OR +# * Just fetches, and collapses/constructs everything as if $fetch_all +# was requested (there is no other way to collapse except for an +# eager cursor) +# * If no collapse is requested - just get the next row, construct and +# return +sub _construct_results { + my ($self, $fetch_all) = @_; - # 'foo' => [ undef, 'foo' ] - # 'foo.bar' => [ 'foo', 'bar' ] - # 'foo.bar.baz' => [ 'foo.bar', 'baz' ] + my $rsrc = $self->result_source; + my $attrs = $self->_resolved_attrs; - my @construct_as = map { [ (/^(?:(.*)\.)?([^.]+)$/) ] } @$as_proto; + if ( + ! $fetch_all + and + ! $attrs->{order_by} + and + $attrs->{collapse} + and + my @pcols = $rsrc->primary_columns + ) { + # default order for collapsing unless the user asked for something + $attrs->{order_by} = [ map { join '.', $attrs->{alias}, $_} @pcols ]; + $attrs->{_ordered_for_collapse} = 1; + $attrs->{_order_is_artificial} = 1; + } - my %collapse = %{$self->{_attrs}{collapse}||{}}; + # this will be used as both initial raw-row collector AND as a RV of + # _construct_results. Not regrowing the array twice matters a lot... + # a surprising amount actually + my $rows = delete $self->{_stashed_rows}; - my @pri_index; + my $cursor; # we may not need one at all - # if we're doing collapsing (has_many prefetch) we need to grab records - # until the PK changes, so fill @pri_index. if not, we leave it empty so - # we know we don't have to bother. + my $did_fetch_all = $fetch_all; - # the reason for not using the collapse stuff directly is because if you - # had for e.g. two artists in a row with no cds, the collapse info for - # both would be NULL (undef) so you'd lose the second artist + if ($fetch_all) { + # FIXME SUBOPTIMAL - we can do better, cursor->next/all (well diff. methods) should return a ref + $rows = [ ($rows ? @$rows : ()), $self->cursor->all ]; + } + elsif( $attrs->{collapse} ) { - # store just the index so we can check the array positions from the row - # without having to contruct the full hash + # a cursor will need to be closed over in case of collapse + $cursor = $self->cursor; - if (keys %collapse) { - my %pri = map { ($_ => 1) } $self->result_source->_pri_cols; - foreach my $i (0 .. $#construct_as) { - next if defined($construct_as[$i][0]); # only self table - if (delete $pri{$construct_as[$i][1]}) { - push(@pri_index, $i); + $attrs->{_ordered_for_collapse} = ( + ( + $attrs->{order_by} + and + $rsrc->schema + ->storage + ->_main_source_order_by_portion_is_stable($rsrc, $attrs->{order_by}, $attrs->{where}) + ) ? 1 : 0 + ) unless defined $attrs->{_ordered_for_collapse}; + + if (! $attrs->{_ordered_for_collapse}) { + $did_fetch_all = 1; + + # instead of looping over ->next, use ->all in stealth mode + # *without* calling a ->reset afterwards + # FIXME ENCAPSULATION - encapsulation breach, cursor method additions pending + if (! $cursor->{_done}) { + $rows = [ ($rows ? @$rows : ()), $cursor->all ]; + $cursor->{_done} = 1; } - last unless keys %pri; # short circuit (Johnny Five Is Alive!) } } - # no need to do an if, it'll be empty if @pri_index is empty anyway + if (! $did_fetch_all and ! @{$rows||[]} ) { + # FIXME SUBOPTIMAL - we can do better, cursor->next/all (well diff. methods) should return a ref + $cursor ||= $self->cursor; + if (scalar (my @r = $cursor->next) ) { + $rows = [ \@r ]; + } + } - my %pri_vals = map { ($_ => $copy[$_]) } @pri_index; + return undef unless @{$rows||[]}; - my @const_rows; + # sanity check - people are too clever for their own good + if ($attrs->{collapse} and my $aliastypes = $attrs->{_sqlmaker_select_args}[3]{_aliastypes} ) { - do { # no need to check anything at the front, we always want the first row + my $multiplied_selectors; + for my $sel_alias ( grep { $_ ne $attrs->{alias} } keys %{ $aliastypes->{selecting} } ) { + if ( + $aliastypes->{multiplying}{$sel_alias} + or + scalar grep { $aliastypes->{multiplying}{(values %$_)[0]} } @{ $aliastypes->{selecting}{$sel_alias}{-parents} } + ) { + $multiplied_selectors->{$_} = 1 for values %{$aliastypes->{selecting}{$sel_alias}{-seen_columns}} + } + } + + for my $i (0 .. $#{$attrs->{as}} ) { + my $sel = $attrs->{select}[$i]; - my %const; + if (ref $sel eq 'SCALAR') { + $sel = $$sel; + } + elsif( ref $sel eq 'REF' and ref $$sel eq 'ARRAY' ) { + $sel = $$sel->[0]; + } - foreach my $this_as (@construct_as) { - $const{$this_as->[0]||''}{$this_as->[1]} = shift(@copy); + $self->throw_exception( + 'Result collapse not possible - selection from a has_many source redirected to the main object' + ) if ($multiplied_selectors->{$sel} and $attrs->{as}[$i] !~ /\./); } + } - push(@const_rows, \%const); + # hotspot - skip the setter + my $res_class = $self->_result_class; - } until ( # no pri_index => no collapse => drop straight out - !@pri_index - or - do { # get another row, stash it, drop out if different PK + my $inflator_cref = $self->{_result_inflator}{cref} ||= do { + $res_class->can ('inflate_result') + or $self->throw_exception("Inflator $res_class does not provide an inflate_result() method"); + }; - @copy = $self->cursor->next; - $self->{stashed_row} = \@copy; + my $infmap = $attrs->{as}; - # last thing in do block, counts as true if anything doesn't match + $self->{_result_inflator}{is_core_row} = ( ( + $inflator_cref + == + ( \&DBIx::Class::Row::inflate_result || die "No ::Row::inflate_result() - can't happen" ) + ) ? 1 : 0 ) unless defined $self->{_result_inflator}{is_core_row}; - # check xor defined first for NULL vs. NOT NULL then if one is - # defined the other must be so check string equality + $self->{_result_inflator}{is_hri} = ( ( + ! $self->{_result_inflator}{is_core_row} + and + $inflator_cref == ( + require DBIx::Class::ResultClass::HashRefInflator + && + DBIx::Class::ResultClass::HashRefInflator->can('inflate_result') + ) + ) ? 1 : 0 ) unless defined $self->{_result_inflator}{is_hri}; - grep { - (defined $pri_vals{$_} ^ defined $copy[$_]) - || (defined $pri_vals{$_} && ($pri_vals{$_} ne $copy[$_])) - } @pri_index; + + if (! $attrs->{_related_results_construction}) { + # construct a much simpler array->hash folder for the one-table cases right here + if ($self->{_result_inflator}{is_hri}) { + for my $r (@$rows) { + $r = { map { $infmap->[$_] => $r->[$_] } 0..$#$infmap }; } - ); + } + # FIXME SUBOPTIMAL this is a very very very hot spot + # while rather optimal we can *still* do much better, by + # building a smarter Row::inflate_result(), and + # switch to feeding it data via a much leaner interface + # + # crude unscientific benchmarking indicated the shortcut eval is not worth it for + # this particular resultset size + elsif (@$rows < 60) { + for my $r (@$rows) { + $r = $inflator_cref->($res_class, $rsrc, { map { $infmap->[$_] => $r->[$_] } (0..$#$infmap) } ); + } + } + else { + eval sprintf ( + '$_ = $inflator_cref->($res_class, $rsrc, { %s }) for @$rows', + join (', ', map { "\$infmap->[$_] => \$_->[$_]" } 0..$#$infmap ) + ); + } + } + else { + my $parser_type = + $self->{_result_inflator}{is_hri} ? 'hri' + : $self->{_result_inflator}{is_core_row} ? 'classic_pruning' + : 'classic_nonpruning' + ; - my $alias = $self->{attrs}{alias}; - my $info = []; + # $args and $attrs to _mk_row_parser are seperated to delineate what is + # core collapser stuff and what is dbic $rs specific + @{$self->{_row_parser}{$parser_type}}{qw(cref nullcheck)} = $rsrc->_mk_row_parser({ + eval => 1, + inflate_map => $infmap, + collapse => $attrs->{collapse}, + premultiplied => $attrs->{_main_source_premultiplied}, + hri_style => $self->{_result_inflator}{is_hri}, + prune_null_branches => $self->{_result_inflator}{is_hri} || $self->{_result_inflator}{is_core_row}, + }, $attrs) unless $self->{_row_parser}{$parser_type}{cref}; + + # column_info metadata historically hasn't been too reliable. + # We need to start fixing this somehow (the collapse resolver + # can't work without it). Add an explicit check for the *main* + # result, hopefully this will gradually weed out such errors + # + # FIXME - this is a temporary kludge that reduces perfromance + # It is however necessary for the time being + my ($unrolled_non_null_cols_to_check, $err); + + if (my $check_non_null_cols = $self->{_row_parser}{$parser_type}{nullcheck} ) { + + $err = + 'Collapse aborted due to invalid ResultSource metadata - the following ' + . 'selections are declared non-nullable but NULLs were retrieved: ' + ; - my %collapse_pos; + my @violating_idx; + COL: for my $i (@$check_non_null_cols) { + ! defined $_->[$i] and push @violating_idx, $i and next COL for @$rows; + } - my @const_keys; + $self->throw_exception( $err . join (', ', map { "'$infmap->[$_]'" } @violating_idx ) ) + if @violating_idx; - foreach my $const (@const_rows) { - scalar @const_keys or do { - @const_keys = sort { length($a) <=> length($b) } keys %$const; - }; - foreach my $key (@const_keys) { - if (length $key) { - my $target = $info; - my @parts = split(/\./, $key); - my $cur = ''; - my $data = $const->{$key}; - foreach my $p (@parts) { - $target = $target->[1]->{$p} ||= []; - $cur .= ".${p}"; - if ($cur eq ".${key}" && (my @ckey = @{$collapse{$cur}||[]})) { - # collapsing at this point and on final part - my $pos = $collapse_pos{$cur}; - CK: foreach my $ck (@ckey) { - if (!defined $pos->{$ck} || $pos->{$ck} ne $data->{$ck}) { - $collapse_pos{$cur} = $data; - delete @collapse_pos{ # clear all positioning for sub-entries - grep { m/^\Q${cur}.\E/ } keys %collapse_pos - }; - push(@$target, []); - last CK; - } - } - } - if (exists $collapse{$cur}) { - $target = $target->[-1]; - } - } - $target->[0] = $data; - } else { - $info->[0] = $const->{$key}; + $unrolled_non_null_cols_to_check = join (',', @$check_non_null_cols); + } + + my $next_cref = + ($did_fetch_all or ! $attrs->{collapse}) ? undef + : defined $unrolled_non_null_cols_to_check ? eval sprintf <<'EOS', $unrolled_non_null_cols_to_check +sub { + # FIXME SUBOPTIMAL - we can do better, cursor->next/all (well diff. methods) should return a ref + my @r = $cursor->next or return; + if (my @violating_idx = grep { ! defined $r[$_] } (%s) ) { + $self->throw_exception( $err . join (', ', map { "'$infmap->[$_]'" } @violating_idx ) ) + } + \@r +} +EOS + : sub { + # FIXME SUBOPTIMAL - we can do better, cursor->next/all (well diff. methods) should return a ref + my @r = $cursor->next or return; + \@r } + ; + + $self->{_row_parser}{$parser_type}{cref}->( + $rows, + $next_cref ? ( $next_cref, $self->{_stashed_rows} = [] ) : (), + ); + + # Special-case multi-object HRI - there is no $inflator_cref pass + unless ($self->{_result_inflator}{is_hri}) { + $_ = $inflator_cref->($res_class, $rsrc, @$_) for @$rows } } - return $info; + # The @$rows check seems odd at first - why wouldn't we want to warn + # regardless? The issue is things like find() etc, where the user + # *knows* only one result will come back. In these cases the ->all + # is not a pessimization, but rather something we actually want + carp_unique( + 'Unable to properly collapse has_many results in iterator mode due ' + . 'to order criteria - performed an eager cursor slurp underneath. ' + . 'Consider using ->all() instead' + ) if ( ! $fetch_all and @$rows > 1 ); + + return $rows; } =head2 result_source @@ -1422,14 +1558,22 @@ in the original source class will not run. sub result_class { my ($self, $result_class) = @_; if ($result_class) { - unless (ref $result_class) { # don't fire this for an object - $self->ensure_class_loaded($result_class); + + # don't fire this for an object + $self->ensure_class_loaded($result_class) + unless ref($result_class); + + if ($self->get_cache) { + carp_unique('Changing the result_class of a ResultSet instance with cached results is a noop - the cache contents will not be altered'); + } + # FIXME ENCAPSULATION - encapsulation breach, cursor method additions pending + elsif ($self->{cursor} && $self->{cursor}{_pos}) { + $self->throw_exception('Changing the result_class of a ResultSet instance with an active cursor is not supported'); } + $self->_result_class($result_class); - # THIS LINE WOULD BE A BUG - this accessor specifically exists to - # permit the user to set result class on one result set only; it only - # chains if provided to search() - #$self->{attrs}{result_class} = $result_class if ref $self; + + delete $self->{_result_inflator}; } $self->_result_class; } @@ -1459,8 +1603,7 @@ sub count { # this is a little optimization - it is faster to do the limit # adjustments in software, instead of a subquery - my $rows = delete $attrs->{rows}; - my $offset = delete $attrs->{offset}; + my ($rows, $offset) = delete @{$attrs}{qw/rows offset/}; my $crs; if ($self->_has_resolved_attr (qw/collapse group_by/)) { @@ -1508,10 +1651,10 @@ sub count_rs { # software based limiting can not be ported if this $rs is to be used # in a subquery itself (i.e. ->as_query) if ($self->_has_resolved_attr (qw/collapse group_by offset rows/)) { - return $self->_count_subq_rs; + return $self->_count_subq_rs($self->{_attrs}); } else { - return $self->_count_rs; + return $self->_count_rs($self->{_attrs}); } } @@ -1522,20 +1665,17 @@ sub _count_rs { my ($self, $attrs) = @_; my $rsrc = $self->result_source; - $attrs ||= $self->_resolved_attrs; my $tmp_attrs = { %$attrs }; # take off any limits, record_filter is cdbi, and no point of ordering nor locking a count delete @{$tmp_attrs}{qw/rows offset order_by record_filter for/}; # overwrite the selector (supplied by the storage) - $tmp_attrs->{select} = $rsrc->storage->_count_select ($rsrc, $attrs); - $tmp_attrs->{as} = 'count'; - delete @{$tmp_attrs}{qw/columns/}; - - my $tmp_rs = $rsrc->resultset_class->new($rsrc, $tmp_attrs)->get_column ('count'); - - return $tmp_rs; + $rsrc->resultset_class->new($rsrc, { + %$tmp_attrs, + select => $rsrc->storage->_count_select ($rsrc, $attrs), + as => 'count', + })->get_column ('count'); } # @@ -1545,15 +1685,14 @@ sub _count_subq_rs { my ($self, $attrs) = @_; my $rsrc = $self->result_source; - $attrs ||= $self->_resolved_attrs; my $sub_attrs = { %$attrs }; # extra selectors do not go in the subquery and there is no point of ordering it, nor locking it - delete @{$sub_attrs}{qw/collapse columns as select _prefetch_selector_range order_by for/}; + delete @{$sub_attrs}{qw/collapse columns as select order_by for/}; # if we multi-prefetch we group_by something unique, as this is what we would # get out of the rs via ->next/->all. We *DO WANT* to clobber old group_by regardless - if ( keys %{$attrs->{collapse}} ) { + if ( $attrs->{collapse} ) { $sub_attrs->{group_by} = [ map { "$attrs->{alias}.$_" } @{ $rsrc->_identifying_column_set || $self->throw_exception( 'Unable to construct a unique group_by criteria properly collapsing the ' @@ -1636,9 +1775,6 @@ sub _count_subq_rs { ->get_column ('count'); } -sub _bool { - return 1; -} =head2 count_literal @@ -1677,33 +1813,22 @@ Returns all elements in the resultset. sub all { my $self = shift; if(@_) { - $self->throw_exception("all() doesn't take any arguments, you probably wanted ->search(...)->all()"); + $self->throw_exception("all() doesn't take any arguments, you probably wanted ->search(...)->all()"); } - return @{ $self->get_cache } if $self->get_cache; - - my @obj; - - if (keys %{$self->_resolved_attrs->{collapse}}) { - # Using $self->cursor->all is really just an optimisation. - # If we're collapsing has_many prefetches it probably makes - # very little difference, and this is cleaner than hacking - # _construct_object to survive the approach - $self->cursor->reset; - my @row = $self->cursor->next; - while (@row) { - push(@obj, $self->_construct_object(@row)); - @row = (exists $self->{stashed_row} - ? @{delete $self->{stashed_row}} - : $self->cursor->next); - } - } else { - @obj = map { $self->_construct_object(@$_) } $self->cursor->all; + delete @{$self}{qw/_stashed_rows _stashed_results/}; + + if (my $c = $self->get_cache) { + return @$c; } - $self->set_cache(\@obj) if $self->{attrs}{cache}; + $self->cursor->reset; - return @obj; + my $objs = $self->_construct_results('fetch_all') || []; + + $self->set_cache($objs) if $self->{attrs}{cache}; + + return @$objs; } =head2 reset @@ -1724,6 +1849,8 @@ another query. sub reset { my ($self) = @_; + + delete @{$self}{qw/_stashed_rows _stashed_results/}; $self->{all_cache_position} = 0; $self->cursor->reset; return $self; @@ -1764,7 +1891,7 @@ sub _rs_update_delete { my $attrs = { %{$self->_resolved_attrs} }; my $join_classifications; - my $existing_group_by = delete $attrs->{group_by}; + my ($existing_group_by) = delete @{$attrs}{qw(group_by _grouped_by_distinct)}; # do we need a subquery for any reason? my $needs_subq = ( @@ -1779,20 +1906,12 @@ sub _rs_update_delete { # simplify the joinmap, so we can further decide if a subq is necessary if (!$needs_subq and @{$attrs->{from}} > 1) { - $attrs->{from} = $storage->_prune_unused_joins ($attrs->{from}, $attrs->{select}, $self->{cond}, $attrs); - - # check if there are any joins left after the prune - if ( @{$attrs->{from}} > 1 ) { - $join_classifications = $storage->_resolve_aliastypes_from_select_args ( - [ @{$attrs->{from}}[1 .. $#{$attrs->{from}}] ], - $attrs->{select}, - $self->{cond}, - $attrs - ); - # any non-pruneable joins imply subq - $needs_subq = scalar keys %{ $join_classifications->{restricting} || {} }; - } + ($attrs->{from}, $join_classifications) = + $storage->_prune_unused_joins ($attrs->{from}, $attrs->{select}, $self->{cond}, $attrs); + + # any non-pruneable non-local restricting joins imply subq + $needs_subq = defined List::Util::first { $_ ne $attrs->{alias} } keys %{ $join_classifications->{restricting} || {} }; } # check if the head is composite (by now all joins are thrown out unless $needs_subq) @@ -1825,9 +1944,12 @@ sub _rs_update_delete { ); # make a new $rs selecting only the PKs (that's all we really need for the subq) - delete $attrs->{$_} for qw/collapse _collapse_order_by select _prefetch_selector_range as/; + delete $attrs->{$_} for qw/select as collapse/; $attrs->{columns} = [ map { "$attrs->{alias}.$_" } @$idcols ]; - $attrs->{group_by} = \ ''; # FIXME - this is an evil hack, it causes the optimiser to kick in and throw away the LEFT joins + + # this will be consumed by the pruner waaaaay down the stack + $attrs->{_force_prune_multiplying_joins} = 1; + my $subrs = (ref $self)->new($rsrc, $attrs); if (@$idcols == 1) { @@ -2261,7 +2383,7 @@ sub pager { # throw away the paging flags and re-run the count (possibly # with a subselect) to get the real total count my $count_attrs = { %$attrs }; - delete $count_attrs->{$_} for qw/rows offset page pager/; + delete @{$count_attrs}{qw/rows offset page pager/}; my $total_rs = (ref $self)->new($self->result_source, $count_attrs); @@ -2324,15 +2446,29 @@ sub new_result { my ($merged_cond, $cols_from_relations) = $self->_merge_with_rscond($values); - my %new = ( + my $new = $self->result_class->new({ %$merged_cond, - @$cols_from_relations + ( @$cols_from_relations ? (-cols_from_relations => $cols_from_relations) - : (), + : () + ), -result_source => $self->result_source, # DO NOT REMOVE THIS, REQUIRED - ); + }); - return $self->result_class->new(\%new); + if ( + reftype($new) eq 'HASH' + and + ! keys %$new + and + blessed($new) + ) { + carp_unique (sprintf ( + "%s->new returned a blessed empty hashref - a strong indicator something is wrong with its inheritance chain", + $self->result_class, + )); + } + + $new; } # _merge_with_rscond @@ -2520,16 +2656,13 @@ sub as_query { my $attrs = { %{ $self->_resolved_attrs } }; - # For future use: - # - # in list ctx: - # my ($sql, \@bind, \%dbi_bind_attrs) = _select_args_to_query (...) - # $sql also has no wrapping parenthesis in list ctx - # - my $sqlbind = $self->result_source->storage - ->_select_args_to_query ($attrs->{from}, $attrs->{select}, $attrs->{where}, $attrs); + my $aq = $self->result_source->storage->_select_args_to_query ( + $attrs->{from}, $attrs->{select}, $attrs->{where}, $attrs + ); - return $sqlbind; + $self->{_attrs}{_sqlmaker_select_args} = $attrs->{_sqlmaker_select_args}; + + $aq; } =head2 find_or_new @@ -2546,7 +2679,7 @@ sub as_query { { artist => 'fred' }, { key => 'artists' }); $cd->cd_to_producer->find_or_new({ producer => $producer }, - { key => 'primary }); + { key => 'primary' }); Find an existing record from this resultset using L. if none exists, instantiate a new result object and return it. The object will not be saved @@ -2661,10 +2794,10 @@ L. =cut sub create { - my ($self, $attrs) = @_; + my ($self, $col_data) = @_; $self->throw_exception( "create needs a hashref" ) - unless ref $attrs eq 'HASH'; - return $self->new_result($attrs)->insert; + unless ref $col_data eq 'HASH'; + return $self->new_result($col_data)->insert; } =head2 find_or_create @@ -3001,8 +3134,10 @@ Returns a related resultset for the supplied relationship name. sub related_resultset { my ($self, $rel) = @_; - $self->{related_resultsets} ||= {}; - return $self->{related_resultsets}{$rel} ||= do { + return $self->{related_resultsets}{$rel} + if defined $self->{related_resultsets}{$rel}; + + return $self->{related_resultsets}{$rel} = do { my $rsrc = $self->result_source; my $rel_info = $rsrc->relationship_info($rel); @@ -3028,15 +3163,6 @@ sub related_resultset { #XXX - temp fix for result_class bug. There likely is a more elegant fix -groditi delete @{$attrs}{qw(result_class alias)}; - my $new_cache; - - if (my $cache = $self->get_cache) { - if ($cache->[0] && $cache->[0]->related_resultset($rel)->get_cache) { - $new_cache = [ map { @{$_->related_resultset($rel)->get_cache} } - @$cache ]; - } - } - my $rel_source = $rsrc->related_source($rel); my $new = do { @@ -3057,7 +3183,16 @@ sub related_resultset { where => $attrs->{where}, }); }; - $new->set_cache($new_cache) if $new_cache; + + if (my $cache = $self->get_cache) { + my @related_cache = map + { @{$_->related_resultset($rel)->get_cache||[]} } + @$cache + ; + + $new->set_cache(\@related_cache) if @related_cache; + } + $new; }; } @@ -3197,7 +3332,7 @@ sub _chain_relationship { # ->_resolve_join as otherwise they get lost - captainL my $join = $self->_merge_joinpref_attr( $attrs->{join}, $attrs->{prefetch} ); - delete @{$attrs}{qw/join prefetch collapse group_by distinct select as columns +select +as +columns/}; + delete @{$attrs}{qw/join prefetch collapse group_by distinct _grouped_by_distinct select as columns +select +as +columns/}; my $seen = { %{ (delete $attrs->{seen_join}) || {} } }; @@ -3327,14 +3462,10 @@ sub _resolved_attrs { if $attrs->{select}; # assume all unqualified selectors to apply to the current alias (legacy stuff) - for (@sel) { - $_ = (ref $_ or $_ =~ /\./) ? $_ : "$alias.$_"; - } + $_ = (ref $_ or $_ =~ /\./) ? $_ : "$alias.$_" for @sel; - # disqualify all $alias.col as-bits (collapser mandated) - for (@as) { - $_ = ($_ =~ /^\Q$alias.\E(.+)$/) ? $1 : $_; - } + # disqualify all $alias.col as-bits (inflate-map mandated) + $_ = ($_ =~ /^\Q$alias.\E(.+)$/) ? $1 : $_ for @as; # de-duplicate the result (remove *identical* select/as pairs) # and also die on duplicate {as} pointing to different {select}s @@ -3411,25 +3542,24 @@ sub _resolved_attrs { carp_unique ("Useless use of distinct on a grouped resultset ('distinct' is ignored when a 'group_by' is present)"); } else { + $attrs->{_grouped_by_distinct} = 1; # distinct affects only the main selection part, not what prefetch may # add below. - $attrs->{group_by} = $source->storage->_group_over_selection ( - $attrs->{from}, - $attrs->{select}, - $attrs->{order_by}, - ); + $attrs->{group_by} = $source->storage->_group_over_selection($attrs); } } - $attrs->{collapse} ||= {}; - if ($attrs->{prefetch}) { + # generate selections based on the prefetch helper + my $prefetch; + $prefetch = $self->_merge_joinpref_attr( {}, delete $attrs->{prefetch} ) + if defined $attrs->{prefetch}; + + if ($prefetch) { $self->throw_exception("Unable to prefetch, resultset contains an unnamed selector $attrs->{_dark_selector}{string}") if $attrs->{_dark_selector}; - my $prefetch = $self->_merge_joinpref_attr( {}, delete $attrs->{prefetch} ); - - my $prefetch_ordering = []; + $attrs->{collapse} = 1; # this is a separate structure (we don't look in {from} directly) # as the resolver needs to shift things off the lists to work @@ -3452,20 +3582,63 @@ sub _resolved_attrs { } } - my @prefetch = - $source->_resolve_prefetch( $prefetch, $alias, $join_map, $prefetch_ordering, $attrs->{collapse} ); - - # we need to somehow mark which columns came from prefetch - if (@prefetch) { - my $sel_end = $#{$attrs->{select}}; - $attrs->{_prefetch_selector_range} = [ $sel_end + 1, $sel_end + @prefetch ]; - } + my @prefetch = $source->_resolve_prefetch( $prefetch, $alias, $join_map ); push @{ $attrs->{select} }, (map { $_->[0] } @prefetch); push @{ $attrs->{as} }, (map { $_->[1] } @prefetch); + } - push( @{$attrs->{order_by}}, @$prefetch_ordering ); - $attrs->{_collapse_order_by} = \@$prefetch_ordering; + if ( List::Util::first { $_ =~ /\./ } @{$attrs->{as}} ) { + $attrs->{_related_results_construction} = 1; + } + + # run through the resulting joinstructure (starting from our current slot) + # and unset collapse if proven unnesessary + # + # also while we are at it find out if the current root source has + # been premultiplied by previous related_source chaining + # + # this allows to predict whether a root object with all other relation + # data set to NULL is in fact unique + if ($attrs->{collapse}) { + + if (ref $attrs->{from} eq 'ARRAY') { + + if (@{$attrs->{from}} == 1) { + # no joins - no collapse + $attrs->{collapse} = 0; + } + else { + # find where our table-spec starts + my @fromlist = @{$attrs->{from}}; + while (@fromlist) { + my $t = shift @fromlist; + + my $is_multi; + # me vs join from-spec distinction - a ref means non-root + if (ref $t eq 'ARRAY') { + $t = $t->[0]; + $is_multi ||= ! $t->{-is_single}; + } + last if ($t->{-alias} && $t->{-alias} eq $alias); + $attrs->{_main_source_premultiplied} ||= $is_multi; + } + + # no non-singles remaining, nor any premultiplication - nothing to collapse + if ( + ! $attrs->{_main_source_premultiplied} + and + ! List::Util::first { ! $_->[0]{-is_single} } @fromlist + ) { + $attrs->{collapse} = 0; + } + } + } + + else { + # if we can not analyze the from - err on the side of safety + $attrs->{_main_source_premultiplied} = 1; + } } # if both page and offset are specified, produce a combined offset @@ -3592,7 +3765,7 @@ sub _merge_joinpref_attr { $seen_keys->{$import_key} = 1; # don't merge the same key twice } - return $orig; + return @$orig ? $orig : (); } { @@ -3688,7 +3861,8 @@ sub STORABLE_freeze { my $to_serialize = { %$self }; # A cursor in progress can't be serialized (and would make little sense anyway) - delete $to_serialize->{cursor}; + # the parser can be regenerated (and can't be serialized) + delete @{$to_serialize}{qw/cursor _row_parser _result_inflator/}; # nor is it sensical to store a not-yet-fired-count pager if ($to_serialize->{pager} and ref $to_serialize->{pager}{total_entries} eq 'CODE') { @@ -3725,6 +3899,10 @@ sub throw_exception { } } +1; + +__END__ + # XXX: FIXME: Attributes docs need clearing up =head1 ATTRIBUTES @@ -3774,7 +3952,7 @@ syntax as outlined above. =over 4 -=item Value: \@columns +=item Value: \@columns | \%columns | $column =back @@ -3784,7 +3962,7 @@ case the key is the C value, and the value is used as the C from that, then auto-populates C from C and L. @@ -3803,10 +3981,10 @@ is the same as =back -Indicates additional columns to be selected from storage. Works the same -as L but adds columns to the selection. (You may also use the -C attribute, as in earlier versions of DBIC). For -example:- +Indicates additional columns to be selected from storage. Works the same as +L but adds columns to the selection. (You may also use the +C attribute, as in earlier versions of DBIC, but this is +deprecated). For example:- $schema->resultset('CD')->search(undef, { '+columns' => ['artist.name'], @@ -3876,14 +4054,6 @@ an explicit list. =back -=head2 +as - -=over 4 - -Indicates additional column names for those added via L. See L. - -=back - =head2 as =over 4 @@ -3926,6 +4096,14 @@ use C instead: You can create your own accessors if required - see L for details. +=head2 +as + +=over 4 + +Indicates additional column names for those added via L. See L. + +=back + =head2 join =over 4 @@ -3989,7 +4167,7 @@ similarly for a third time). For e.g. will return a set of all artists that have both a cd with title 'Down to Earth' and a cd with title 'Popular'. -If you want to fetch related objects from other tables as well, see C +If you want to fetch related objects from other tables as well, see L below. NOTE: An internal join-chain pruner will discard certain joins while @@ -4000,185 +4178,133 @@ below. For more help on using joins with search, see L. -=head2 prefetch +=head2 collapse =over 4 -=item Value: ($rel_name | \@rel_names | \%rel_names) +=item Value: (0 | 1) =back -Contains one or more relationships that should be fetched along with -the main query (when they are accessed afterwards the data will -already be available, without extra queries to the database). This is -useful for when you know you will need the related objects, because it -saves at least one query: - - my $rs = $schema->resultset('Tag')->search( - undef, - { - prefetch => { - cd => 'artist' - } - } - ); - -The initial search results in SQL like the following: - - SELECT tag.*, cd.*, artist.* FROM tag - JOIN cd ON tag.cd = cd.cdid - JOIN artist ON cd.artist = artist.artistid - -L has no need to go back to the database when we access the -C or C relationships, which saves us two SQL statements in this -case. - -Simple prefetches will be joined automatically, so there is no need -for a C attribute in the above search. - -L can be used with the any of the relationship types and -multiple prefetches can be specified together. Below is a more complex -example that prefetches a CD's artist, its liner notes (if present), -the cover image, the tracks on that cd, and the guests on those -tracks. - - # Assuming: - My::Schema::CD->belongs_to( artist => 'My::Schema::Artist' ); - My::Schema::CD->might_have( liner_note => 'My::Schema::LinerNotes' ); - My::Schema::CD->has_one( cover_image => 'My::Schema::Artwork' ); - My::Schema::CD->has_many( tracks => 'My::Schema::Track' ); - - My::Schema::Artist->belongs_to( record_label => 'My::Schema::RecordLabel' ); - - My::Schema::Track->has_many( guests => 'My::Schema::Guest' ); - - - my $rs = $schema->resultset('CD')->search( - undef, - { - prefetch => [ - { artist => 'record_label'}, # belongs_to => belongs_to - 'liner_note', # might_have - 'cover_image', # has_one - { tracks => 'guests' }, # has_many => has_many - ] - } - ); - -This will produce SQL like the following: - - SELECT cd.*, artist.*, record_label.*, liner_note.*, cover_image.*, - tracks.*, guests.* - FROM cd me - JOIN artist artist - ON artist.artistid = me.artistid - JOIN record_label record_label - ON record_label.labelid = artist.labelid - LEFT JOIN track tracks - ON tracks.cdid = me.cdid - LEFT JOIN guest guests - ON guests.trackid = track.trackid - LEFT JOIN liner_notes liner_note - ON liner_note.cdid = me.cdid - JOIN cd_artwork cover_image - ON cover_image.cdid = me.cdid - ORDER BY tracks.cd - -Now the C, C, C, C, -C, and C of the CD will all be available through the -relationship accessors without the need for additional queries to the -database. - -However, there is one caveat to be observed: it can be dangerous to -prefetch more than one L -relationship on a given level. e.g.: - - my $rs = $schema->resultset('CD')->search( - undef, - { - prefetch => [ - 'tracks', # has_many - { cd_to_producer => 'producer' }, # has_many => belongs_to (i.e. m2m) - ] - } - ); +When set to a true value, indicates that any rows fetched from joined has_many +relationships are to be aggregated into the corresponding "parent" object. For +example, the resultset: -The collapser currently can't identify duplicate tuples for multiple -L relationships and as a -result the second L -relation could contain redundant objects. - -=head3 Using L with L - -L implies a L with the equivalent argument, and is -properly merged with any existing L specification. So the -following: + my $rs = $schema->resultset('CD')->search({}, { + '+columns' => [ qw/ tracks.title tracks.position / ], + join => 'tracks', + collapse => 1, + }); - my $rs = $schema->resultset('CD')->search( - {'record_label.name' => 'Music Product Ltd.'}, - { - join => {artist => 'record_label'}, - prefetch => 'artist', - } - ); +While executing the following query: -... will work, searching on the record label's name, but only -prefetching the C. + SELECT me.*, tracks.title, tracks.position + FROM cd me + LEFT JOIN track tracks + ON tracks.cdid = me.cdid -=head3 Using L with L / L / L / L +Will return only as many objects as there are rows in the CD source, even +though the result of the query may span many rows. Each of these CD objects +will in turn have multiple "Track" objects hidden behind the has_many +generated accessor C. Without C<< collapse => 1 >>, the return values +of this resultset would be as many CD objects as there are tracks (a "Cartesian +product"), with each CD object containing exactly one of all fetched Track data. -L implies a L/L with the fields of the -prefetched relations. So given: +When a collapse is requested on a non-ordered resultset, an order by some +unique part of the main source (the left-most table) is inserted automatically. +This is done so that the resultset is allowed to be "lazy" - calling +L<< $rs->next|/next >> will fetch only as many rows as it needs to build the next +object with all of its related data. - my $rs = $schema->resultset('CD')->search( - undef, - { - select => ['cd.title'], - as => ['cd_title'], - prefetch => 'artist', - } - ); +If an L is already declared, and orders the resultset in a way that +makes collapsing as described above impossible (e.g. C<< ORDER BY +has_many_rel.column >> or C), DBIC will automatically +switch to "eager" mode and slurp the entire resultset before consturcting the +first object returned by L. -The L becomes: C<'cd.title', 'artist.*'> and the L -becomes: C<'cd_title', 'artist.*'>. +Setting this attribute on a resultset that does not join any has_many +relations is a no-op. -=head3 CAVEATS +For a more in-depth discussion, see L. -Prefetch does a lot of deep magic. As such, it may not behave exactly -as you might expect. +=head2 prefetch =over 4 -=item * - -Prefetch uses the L to populate the prefetched relationships. This -may or may not be what you want. +=item Value: ($rel_name | \@rel_names | \%rel_names) -=item * +=back -If you specify a condition on a prefetched relationship, ONLY those -rows that match the prefetched condition will be fetched into that relationship. -This means that adding prefetch to a search() B what is returned by -traversing a relationship. So, if you have C<< Artist->has_many(CDs) >> and you do +This attribute is a shorthand for specifying a L spec, adding all +columns from the joined related sources as L and setting +L to a true value. For example, the following two queries are +equivalent: - my $artist_rs = $schema->resultset('Artist')->search({ - 'cds.year' => 2008, - }, { - join => 'cds', + my $rs = $schema->resultset('Artist')->search({}, { + prefetch => { cds => ['genre', 'tracks' ] }, }); - my $count = $artist_rs->first->cds->count; +and - my $artist_rs_prefetch = $artist_rs->search( {}, { prefetch => 'cds' } ); + my $rs = $schema->resultset('Artist')->search({}, { + join => { cds => ['genre', 'tracks' ] }, + collapse => 1, + '+columns' => [ + (map + { +{ "cds.$_" => "cds.$_" } } + $schema->source('Artist')->related_source('cds')->columns + ), + (map + { +{ "cds.genre.$_" => "genre.$_" } } + $schema->source('Artist')->related_source('cds')->related_source('genre')->columns + ), + (map + { +{ "cds.tracks.$_" => "tracks.$_" } } + $schema->source('Artist')->related_source('cds')->related_source('tracks')->columns + ), + ], + }); - my $prefetch_count = $artist_rs_prefetch->first->cds->count; +Both producing the following SQL: + + SELECT me.artistid, me.name, me.rank, me.charfield, + cds.cdid, cds.artist, cds.title, cds.year, cds.genreid, cds.single_track, + genre.genreid, genre.name, + tracks.trackid, tracks.cd, tracks.position, tracks.title, tracks.last_updated_on, tracks.last_updated_at + FROM artist me + LEFT JOIN cd cds + ON cds.artist = me.artistid + LEFT JOIN genre genre + ON genre.genreid = cds.genreid + LEFT JOIN track tracks + ON tracks.cd = cds.cdid + ORDER BY me.artistid + +While L implies a L, it is ok to mix the two together, as +the arguments are properly merged and generally do the right thing. For +example, you may want to do the following: + + my $artists_and_cds_without_genre = $schema->resultset('Artist')->search( + { 'genre.genreid' => undef }, + { + join => { cds => 'genre' }, + prefetch => 'cds', + } + ); - cmp_ok( $count, '==', $prefetch_count, "Counts should be the same" ); +Which generates the following SQL: -that cmp_ok() may or may not pass depending on the datasets involved. This -behavior may or may not survive the 0.09 transition. + SELECT me.artistid, me.name, me.rank, me.charfield, + cds.cdid, cds.artist, cds.title, cds.year, cds.genreid, cds.single_track + FROM artist me + LEFT JOIN cd cds + ON cds.artist = me.artistid + LEFT JOIN genre genre + ON genre.genreid = cds.genreid + WHERE genre.genreid IS NULL + ORDER BY me.artistid -=back +For a more in-depth discussion, see L. =head2 alias @@ -4356,6 +4482,131 @@ Set to 'update' for a SELECT ... FOR UPDATE or 'shared' for a SELECT ... FOR SHARED. If \$scalar is passed, this is taken directly and embedded in the query. +=head1 PREFETCHING + +DBIx::Class supports arbitrary related data prefetching from multiple related +sources. Any combination of relationship types and column sets are supported. +If L is requested, there is an additional requirement of +selecting enough data to make every individual object uniquely identifiable. + +Here are some more involved examples, based on the following relationship map: + + # Assuming: + My::Schema::CD->belongs_to( artist => 'My::Schema::Artist' ); + My::Schema::CD->might_have( liner_note => 'My::Schema::LinerNotes' ); + My::Schema::CD->has_many( tracks => 'My::Schema::Track' ); + + My::Schema::Artist->belongs_to( record_label => 'My::Schema::RecordLabel' ); + + My::Schema::Track->has_many( guests => 'My::Schema::Guest' ); + + + + my $rs = $schema->resultset('Tag')->search( + undef, + { + prefetch => { + cd => 'artist' + } + } + ); + +The initial search results in SQL like the following: + + SELECT tag.*, cd.*, artist.* FROM tag + JOIN cd ON tag.cd = cd.cdid + JOIN artist ON cd.artist = artist.artistid + +L has no need to go back to the database when we access the +C or C relationships, which saves us two SQL statements in this +case. + +Simple prefetches will be joined automatically, so there is no need +for a C attribute in the above search. + +The L attribute can be used with any of the relationship types +and multiple prefetches can be specified together. Below is a more complex +example that prefetches a CD's artist, its liner notes (if present), +the cover image, the tracks on that CD, and the guests on those +tracks. + + my $rs = $schema->resultset('CD')->search( + undef, + { + prefetch => [ + { artist => 'record_label'}, # belongs_to => belongs_to + 'liner_note', # might_have + 'cover_image', # has_one + { tracks => 'guests' }, # has_many => has_many + ] + } + ); + +This will produce SQL like the following: + + SELECT cd.*, artist.*, record_label.*, liner_note.*, cover_image.*, + tracks.*, guests.* + FROM cd me + JOIN artist artist + ON artist.artistid = me.artistid + JOIN record_label record_label + ON record_label.labelid = artist.labelid + LEFT JOIN track tracks + ON tracks.cdid = me.cdid + LEFT JOIN guest guests + ON guests.trackid = track.trackid + LEFT JOIN liner_notes liner_note + ON liner_note.cdid = me.cdid + JOIN cd_artwork cover_image + ON cover_image.cdid = me.cdid + ORDER BY tracks.cd + +Now the C, C, C, C, +C, and C of the CD will all be available through the +relationship accessors without the need for additional queries to the +database. + +=head3 CAVEATS + +Prefetch does a lot of deep magic. As such, it may not behave exactly +as you might expect. + +=over 4 + +=item * + +Prefetch uses the L to populate the prefetched relationships. This +may or may not be what you want. + +=item * + +If you specify a condition on a prefetched relationship, ONLY those +rows that match the prefetched condition will be fetched into that relationship. +This means that adding prefetch to a search() B what is returned by +traversing a relationship. So, if you have C<< Artist->has_many(CDs) >> and you do + + my $artist_rs = $schema->resultset('Artist')->search({ + 'cds.year' => 2008, + }, { + join => 'cds', + }); + + my $count = $artist_rs->first->cds->count; + + my $artist_rs_prefetch = $artist_rs->search( {}, { prefetch => 'cds' } ); + + my $prefetch_count = $artist_rs_prefetch->first->cds->count; + + cmp_ok( $count, '==', $prefetch_count, "Counts should be the same" ); + +That cmp_ok() may or may not pass depending on the datasets involved. In other +words the C condition would apply to the entire dataset, just like +it would in regular SQL. If you want to add a condition only to the "right side" +of a C - consider declaring and using a L + +=back + =head1 DBIC BIND VALUES Because DBIC may need more information to bind values than just the column name @@ -4403,6 +4654,7 @@ supported: [ $name => $val ] === [ { dbic_colname => $name }, $val ] [ \$dt => $val ] === [ { sqlt_datatype => $dt }, $val ] [ undef, $val ] === [ {}, $val ] + $val === [ {}, $val ] =head1 AUTHOR AND CONTRIBUTORS @@ -4412,6 +4664,3 @@ See L and L in You may distribute this code under the same terms as Perl itself. -=cut - -1;