X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FResultSet.pm;h=c799da79395c6a2c6a4ac714c2e66e8fe3a71c8a;hb=83d2991997f6070366d3d2bcd3f1bcc07562b930;hp=4fff77e21734a826bbb6f5a5f4722c1555e90c09;hpb=95e410363af05aa8a39ec5febc185e18600f69f8;p=dbsrgits%2FDBIx-Class.git diff --git a/lib/DBIx/Class/ResultSet.pm b/lib/DBIx/Class/ResultSet.pm index 4fff77e..c799da7 100644 --- a/lib/DBIx/Class/ResultSet.pm +++ b/lib/DBIx/Class/ResultSet.pm @@ -5,7 +5,8 @@ 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 DBIx::Class::_Util 'fail_on_internal_wantarray'; use Try::Tiny; use Data::Compare (); # no imports!!! guard against insane architecture @@ -25,6 +26,10 @@ 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 +142,15 @@ 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 (e.g.: +C<< my $new_rs = $old_rs->search(\%extra_cond, \%attrs) >>), conditions +and attributes with the same keys need resolving. + +If any of L, L, L are present, they reset the +original selection, and start the selection "clean". -L, L, L, L attributes are merged -into the existing ones from the original resultset. +The L, L, L, L, L attributes +are merged into the existing ones from the original resultset. The L and L attributes, and any search conditions, are merged with an SQL C to the existing condition from the original @@ -236,7 +245,9 @@ sub new { my ($source, $attrs) = @_; $source = $source->resolve if $source->isa('DBIx::Class::ResultSourceHandle'); + $attrs = { %{$attrs||{}} }; + delete @{$attrs}{qw(_last_sqlmaker_alias_map _related_results_construction)}; if ($attrs->{page}) { $attrs->{rows} ||= 10; @@ -294,8 +305,8 @@ 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 +L. For a complete +documentation for the first argument, see L and its extension L. For more help on using joins with search, see L. @@ -317,6 +328,7 @@ sub search { my $rs = $self->search_rs( @_ ); if (wantarray) { + DBIx::Class::_ENV_::ASSERT_NO_INTERNAL_WANTARRAY and my $sog = fail_on_internal_wantarray($rs); return $rs->all; } elsif (defined wantarray) { @@ -389,18 +401,17 @@ sub search_rs { my $cache; my %safe = (alias => 1, cache => 1); if ( ! List::Util::first { !$safe{$_} } keys %$call_attrs and ( - ! defined $_[0] + ! defined $call_cond or - ref $_[0] eq 'HASH' && ! keys %{$_[0]} + ref $call_cond eq 'HASH' && ! keys %$call_cond or - ref $_[0] eq 'ARRAY' && ! @{$_[0]} + ref $call_cond eq 'ARRAY' && ! @$call_cond )) { $cache = $self->get_cache; } 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 +446,7 @@ 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 +493,12 @@ 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 @@ -632,7 +648,7 @@ should only be used in that context. C is a convenience method. It is equivalent to calling C<< $schema->search(\[]) >>, but if you want to ensure columns are bound correctly, use L. -See L and +See L and L for searching techniques that do not require C. @@ -990,7 +1006,7 @@ 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 ); @@ -1049,7 +1065,7 @@ sub single { my $attrs = { %{$self->_resolved_attrs} }; $self->throw_exception( - 'single() can not be used on resultsets prefetching has_many. Use find( \%cond ) or next() instead' + 'single() can not be used on resultsets collapsing a has_many. Use find( \%cond ) or next() instead' ) if $attrs->{collapse}; if ($where) { @@ -1068,9 +1084,10 @@ sub single { $attrs->{from}, $attrs->{select}, $attrs->{where}, $attrs )]; + return undef unless @$data; - $self->{stashed_rows} = [ $data ]; - $self->_construct_objects->[0]; + $self->{_stashed_rows} = [ $data ]; + $self->_construct_results->[0]; } @@ -1196,8 +1213,6 @@ sub slice { $attrs->{offset} += $min; $attrs->{rows} = ($max ? ($max - $min + 1) : 1); return $self->search(undef, $attrs); - #my $slice = (ref $self)->new($self->result_source, $attrs); - #return (wantarray ? $slice->all : $slice); } =head2 next @@ -1239,147 +1254,270 @@ sub next { return ($self->all)[0]; } - return shift(@{$self->{stashed_objects}}) if @{ $self->{stashed_objects}||[] }; + return shift(@{$self->{_stashed_results}}) if @{ $self->{_stashed_results}||[] }; - $self->{stashed_objects} = $self->_construct_objects + $self->{_stashed_results} = $self->_construct_results or return undef; - return shift @{$self->{stashed_objects}}; + return shift @{$self->{_stashed_results}}; } -# Constructs as many objects as it can in one pass while respecting +# Constructs as many results as it can in one pass while respecting # cursor laziness. Several modes of operation: # -# * Always builds everything present in @{$self->{stashed_rows}} +# * Always builds everything present in @{$self->{_stashed_rows}} # * If called with $fetch_all true - pulls everything off the cursor and -# builds all objects in one pass +# 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}} +# and saves the last extra row (if any) in @{$self->{_stashed_rows}} # OR # * Just fetches, and collapses/constructs everything as if $fetch_all # was requested (there is no other way to collapse except for an # eager cursor) # * If no collapse is requested - just get the next row, construct and # return -sub _construct_objects { +sub _construct_results { my ($self, $fetch_all) = @_; my $rsrc = $self->result_source; my $attrs = $self->_resolved_attrs; - my $cursor = $self->cursor; + + 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; + } # this will be used as both initial raw-row collector AND as a RV of - # _construct_objects. Not regrowing the array twice matters a lot... - # a suprising amount actually - my $rows = (delete $self->{stashed_rows}) || []; + # _construct_results. Not regrowing the array twice matters a lot... + # a surprising amount actually + my $rows = delete $self->{_stashed_rows}; + + my $cursor; # we may not need one at all + + my $did_fetch_all = $fetch_all; + if ($fetch_all) { # FIXME SUBOPTIMAL - we can do better, cursor->next/all (well diff. methods) should return a ref - $rows = [ @$rows, $cursor->all ]; + $rows = [ ($rows ? @$rows : ()), $self->cursor->all ]; } - elsif (!$attrs->{collapse}) { + elsif( $attrs->{collapse} ) { + + # a cursor will need to be closed over in case of collapse + $cursor = $self->cursor; + + $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; + } + } + } + + if (! $did_fetch_all and ! @{$rows||[]} ) { # FIXME SUBOPTIMAL - we can do better, cursor->next/all (well diff. methods) should return a ref - push @$rows, do { my @r = $cursor->next; @r ? \@r : () } - unless @$rows; + $cursor ||= $self->cursor; + if (scalar (my @r = $cursor->next) ) { + $rows = [ \@r ]; + } } - else { - $attrs->{_ordered_for_collapse} ||= (!$attrs->{order_by}) ? undef : do { - my $st = $rsrc->schema->storage; - my @ord_cols = map - { $_->[0] } - ( $st->_extract_order_criteria($attrs->{order_by}) ) - ; - my $colinfos = $st->_resolve_column_info($attrs->{from}, \@ord_cols); + return undef unless @{$rows||[]}; - for (0 .. $#ord_cols) { - if ( - ! $colinfos->{$ord_cols[$_]} - or - $colinfos->{$ord_cols[$_]}{-result_source} != $rsrc - ) { - splice @ord_cols, $_; - last; - } + # sanity check - people are too clever for their own good + if ($attrs->{collapse} and my $aliastypes = $attrs->{_last_sqlmaker_alias_map} ) { + + my $multiplied_selectors; + for my $sel_alias ( grep { $_ ne $attrs->{alias} } keys %{ $aliastypes->{selecting} } ) { + if ( + $aliastypes->{multiplying}{$sel_alias} + or + $aliastypes->{premultiplied}{$sel_alias} + ) { + $multiplied_selectors->{$_} = 1 for values %{$aliastypes->{selecting}{$sel_alias}{-seen_columns}} } + } - # since all we check here are the start of the order_by belonging to the - # top level $rsrc, a present identifying set will mean that the resultset - # is ordered by its leftmost table in a tsable manner - (@ord_cols and $rsrc->_identifying_column_set({ map - { $colinfos->{$_}{-colname} => $colinfos->{$_} } - @ord_cols - })) ? 1 : 0; - }; + for my $i (0 .. $#{$attrs->{as}} ) { + my $sel = $attrs->{select}[$i]; - if ($attrs->{_ordered_for_collapse}) { - push @$rows, do { my @r = $cursor->next; @r ? \@r : () }; - } - # instead of looping over ->next, use ->all in stealth mode - # *without* calling a ->reset afterwards - # FIXME - encapsulation breach, got to be a better way - elsif (! $cursor->{_done}) { - push @$rows, $cursor->all; - $cursor->{_done} = 1; - $fetch_all = 1; + if (ref $sel eq 'SCALAR') { + $sel = $$sel; + } + elsif( ref $sel eq 'REF' and ref $$sel eq 'ARRAY' ) { + $sel = $$sel->[0]; + } + + $self->throw_exception( + 'Result collapse not possible - selection from a has_many source redirected to the main object' + ) if ($multiplied_selectors->{$sel} and $attrs->{as}[$i] !~ /\./); } } - return undef unless @$rows; + # hotspot - skip the setter + my $res_class = $self->_result_class; - my $res_class = $self->result_class; - my $inflator = $res_class->can ('inflate_result') - or $self->throw_exception("Inflator $res_class does not provide an inflate_result() method"); + 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"); + }; my $infmap = $attrs->{as}; - if (!$attrs->{collapse} and $attrs->{_single_object_inflation}) { - # construct a much simpler array->hash folder for the one-table cases right here + $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}; + + $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}; + + 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|HRI]::inflate_result(), and + # 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 - if (@$rows < 60) { - my @as_idx = 0..$#$infmap; + elsif (@$rows < 60) { for my $r (@$rows) { - $r = $inflator->($res_class, $rsrc, { map { $infmap->[$_] => $r->[$_] } @as_idx } ); + $r = $inflator_cref->($res_class, $rsrc, { map { $infmap->[$_] => $r->[$_] } (0..$#$infmap) } ); } } else { eval sprintf ( - '$_ = $inflator->($res_class, $rsrc, { %s }) for @$rows', + '$_ = $inflator_cref->($res_class, $rsrc, { %s }) for @$rows', join (', ', map { "\$infmap->[$_] => \$_->[$_]" } 0..$#$infmap ) ); } } else { - $self->{_row_parser} ||= eval sprintf 'sub { %s }', $rsrc->_mk_row_parser({ + my $parser_type = + $self->{_result_inflator}{is_hri} ? 'hri' + : $self->{_result_inflator}{is_core_row} ? 'classic_pruning' + : 'classic_nonpruning' + ; + + # $args and $attrs to _mk_row_parser are separated 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, - selection => $attrs->{select}, collapse => $attrs->{collapse}, premultiplied => $attrs->{_main_source_premultiplied}, - }) or die $@; + 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 performance + # It is however necessary for the time being + my ($unrolled_non_null_cols_to_check, $err); - # modify $rows in-place, shrinking/extending as necessary - $self->{_row_parser}->($rows, $fetch_all ? () : ( - # FIXME SUBOPTIMAL - we can do better, cursor->next/all (well diff. methods) should return a ref - sub { my @r = $cursor->next or return; \@r }, # how the collapser gets more rows - ($self->{stashed_rows} = []), # where does it stuff excess - )); + if (my $check_non_null_cols = $self->{_row_parser}{$parser_type}{nullcheck} ) { - $_ = $inflator->($res_class, $rsrc, @$_) for @$rows; + $err = + 'Collapse aborted due to invalid ResultSource metadata - the following ' + . 'selections are declared non-nullable but NULLs were retrieved: ' + ; + + my @violating_idx; + COL: for my $i (@$check_non_null_cols) { + ! defined $_->[$i] and push @violating_idx, $i and next COL for @$rows; + } + + $self->throw_exception( $err . join (', ', map { "'$infmap->[$_]'" } @violating_idx ) ) + if @violating_idx; + + $unrolled_non_null_cols_to_check = join (',', @$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, $self->{_stashed_rows} = [] ) : (), + ); - # CDBI compat stuff - if ($attrs->{record_filter}) { - $_ = $attrs->{record_filter}->($_) for @$rows; + # Special-case multi-object HRI - there is no $inflator_cref pass + unless ($self->{_result_inflator}{is_hri}) { + $_ = $inflator_cref->($res_class, $rsrc, @$_) for @$rows + } } + # The @$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 $rows; } @@ -1420,14 +1558,22 @@ in the original source class will not run. sub result_class { my ($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; } @@ -1505,10 +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}); } } @@ -1519,19 +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'; - - 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, $attrs), + as => 'count', + })->get_column ('count'); } # @@ -1541,11 +1685,10 @@ sub _count_subq_rs { my ($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 @@ -1632,9 +1775,6 @@ sub _count_subq_rs { ->get_column ('count'); } -sub _bool { - return 1; -} =head2 count_literal @@ -1676,7 +1816,7 @@ sub all { $self->throw_exception("all() doesn't take any arguments, you probably wanted ->search(...)->all()"); } - delete @{$self}{qw/stashed_rows stashed_objects/}; + delete @{$self}{qw/_stashed_rows _stashed_results/}; if (my $c = $self->get_cache) { return @$c; @@ -1684,7 +1824,7 @@ sub all { $self->cursor->reset; - my $objs = $self->_construct_objects('fetch_all') || []; + my $objs = $self->_construct_results('fetch_all') || []; $self->set_cache($objs) if $self->{attrs}{cache}; @@ -1710,7 +1850,7 @@ another query. sub reset { my ($self) = @_; - delete @{$self}{qw/stashed_rows stashed_objects/}; + delete @{$self}{qw/_stashed_rows _stashed_results/}; $self->{all_cache_position} = 0; $self->cursor->reset; return $self; @@ -1751,7 +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 $needs_subq = ( @@ -1766,20 +1906,12 @@ sub _rs_update_delete { # simplify the joinmap, so we can further decide if a subq is necessary if (!$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); + + # 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) @@ -1812,9 +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 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) { @@ -1835,6 +1970,8 @@ sub _rs_update_delete { if ( $existing_group_by or + # we do not need to check pre-multipliers, since if the premulti is there, its + # parent (who is multi) will be there too keys %{ $join_classifications->{multiplying} || {} } ) { # make sure if there is a supplied group_by it matches the columns compiled above @@ -2054,7 +2191,7 @@ first element should be a list of column names and each subsequent element should be a data value in the earlier specified column order. For example: - $Arstist_rs->populate([ + $schema->resultset("Artist")->populate([ [ qw( artistid name ) ], [ 100, 'A Formally Unknown Singer' ], [ 101, 'A singer that jumped the shark two albums ago' ], @@ -2188,7 +2325,7 @@ sub populate { } -# populate() argumnets went over several incarnations +# populate() arguments went over several incarnations # What we ultimately support is AoH sub _normalize_populate_args { my ($self, $arg) = @_; @@ -2311,15 +2448,29 @@ sub new_result { my ($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 @@ -2348,7 +2499,7 @@ sub _merge_with_rscond { ); } else { - # precendence must be given to passed values over values inherited from + # precedence must be given to passed values over values inherited from # the cond, so the order here is important. my $collapsed_cond = $self->_collapse_cond($self->{cond}); my %implied = %{$self->_remove_alias($collapsed_cond, $alias)}; @@ -2383,7 +2534,7 @@ sub _merge_with_rscond { # determines if the resultset defines at least one # of the attributes supplied # -# used to determine if a subquery is neccessary +# used to determine if a subquery is necessary # # supports some virtual attributes: # -join @@ -2507,16 +2658,11 @@ 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; + $aq; } =head2 find_or_new @@ -2533,7 +2679,7 @@ sub as_query { { artist => 'fred' }, { key => 'artists' }); $cd->cd_to_producer->find_or_new({ producer => $producer }, - { key => 'primary }); + { key => 'primary' }); Find an existing record from this resultset using L. if none exists, instantiate a new result object and return it. The object will not be saved @@ -2648,10 +2794,10 @@ L. =cut sub create { - my ($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 @@ -2988,8 +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); @@ -3015,15 +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 { @@ -3044,7 +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 + ; + + $new->set_cache([ map @$_, @related_cache ]) if @related_cache == @$cache; + } + $new; }; } @@ -3184,7 +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 $attrs->{seen_join}) || {} } }; @@ -3269,40 +3417,6 @@ sub _chain_relationship { return {%$attrs, from => $from, seen_join => $seen}; } -# FIXME - this needs to go live in Schema with the tree walker... or -# something -my $inflatemap_checker; -$inflatemap_checker = sub { - my ($rsrc, $relpaths) = @_; - - my $rels; - - for (@$relpaths) { - $_ =~ /^ ( [^\.]+ ) \. (.+) $/x - or next; - - push @{$rels->{$1}}, $2; - } - - for my $rel (keys %$rels) { - my $rel_rsrc = try { - $rsrc->related_source ($rel) - } catch { - $rsrc->throw_exception(sprintf( - "Inflation into non-existent relationship '%s' of '%s' requested, " - . "check the inflation specification (columns/as) ending in '...%s.%s'", - $rel, - $rsrc->source_name, - $rel, - ( sort { length($a) <=> length ($b) } @{$rels->{$rel}} )[0], - ))}; - - $inflatemap_checker->($rel_rsrc, $rels->{$rel}); - } - - return; -}; - sub _resolved_attrs { my $self = shift; return $self->{_attrs} if $self->{_attrs}; @@ -3311,6 +3425,9 @@ sub _resolved_attrs { my $source = $self->result_source; my $alias = $attrs->{alias}; + $self->throw_exception("Specifying distinct => 1 in conjunction with collapse => 1 is unsupported") + if $attrs->{collapse} and $attrs->{distinct}; + # default selection list $attrs->{columns} = [ $source->columns ] unless List::Util::first { exists $attrs->{$_} } qw/columns cols select as/; @@ -3374,14 +3491,6 @@ sub _resolved_attrs { } } - # validate the user-supplied 'as' chain - # folks get too confused by the (logical) exception message, need to - # go to some lengths to clarify the text - # - # FIXME - this needs to go live in Schema with the tree walker... or - # something - $inflatemap_checker->($source, \@as); - $attrs->{select} = \@sel; $attrs->{as} = \@as; @@ -3429,25 +3538,9 @@ sub _resolved_attrs { $attrs->{group_by} = [ $attrs->{group_by} ]; } - # generate the distinct induced group_by early, as prefetch will be carried via a - # subquery (since a group_by is present) - if (delete $attrs->{distinct}) { - if ($attrs->{group_by}) { - carp_unique ("Useless use of distinct on a grouped resultset ('distinct' is ignored when a 'group_by' is present)"); - } - else { - # 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}, - ); - } - } # generate selections based on the prefetch helper - my $prefetch; + my ($prefetch, @prefetch_select, @prefetch_as); $prefetch = $self->_merge_joinpref_attr( {}, delete $attrs->{prefetch} ) if defined $attrs->{prefetch}; @@ -3456,6 +3549,9 @@ sub _resolved_attrs { $self->throw_exception("Unable to prefetch, resultset contains an unnamed selector $attrs->{_dark_selector}{string}") if $attrs->{_dark_selector}; + $self->throw_exception("Specifying prefetch in conjunction with an explicit collapse => 0 is unsupported") + if defined $attrs->{collapse} and ! $attrs->{collapse}; + $attrs->{collapse} = 1; # this is a separate structure (we don't look in {from} directly) @@ -3481,23 +3577,13 @@ sub _resolved_attrs { my @prefetch = $source->_resolve_prefetch( $prefetch, $alias, $join_map ); - # 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 ]; - } - - push @{ $attrs->{select} }, (map { $_->[0] } @prefetch); - push @{ $attrs->{as} }, (map { $_->[1] } @prefetch); - } - - if ( ! List::Util::first { $_ =~ /\./ } @{$attrs->{as}} ) { - $attrs->{_single_object_inflation} = 1; - $attrs->{collapse} = 0; + # save these for after distinct resolution + @prefetch_select = map { $_->[0] } @prefetch; + @prefetch_as = map { $_->[1] } @prefetch; } # run through the resulting joinstructure (starting from our current slot) - # and unset collapse if proven unnesessary + # and unset collapse if proven unnecessary # # also while we are at it find out if the current root source has # been premultiplied by previous related_source chaining @@ -3508,7 +3594,7 @@ sub _resolved_attrs { if (ref $attrs->{from} eq 'ARRAY') { - if (@{$attrs->{from}} <= 1) { + if (@{$attrs->{from}} == 1) { # no joins - no collapse $attrs->{collapse} = 0; } @@ -3545,11 +3631,32 @@ sub _resolved_attrs { } } - if (! $attrs->{order_by} and $attrs->{collapse}) { - # default order for collapsing unless the user asked for something - $attrs->{order_by} = [ map { "$alias.$_" } $source->primary_columns ]; - $attrs->{_ordered_for_collapse} = 1; - $attrs->{_order_is_artificial} = 1; + # generate the distinct induced group_by before injecting the prefetched select/as parts + if (delete $attrs->{distinct}) { + if ($attrs->{group_by}) { + 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}, my $new_order) = $source->storage->_group_over_selection($attrs); + + # FIXME possibly ignore a rewritten order_by (may turn out to be an issue) + # The thinking is: if we are collapsing the subquerying prefetch engine will + # rip stuff apart for us anyway, and we do not want to have a potentially + # function-converted external order_by + # ( there is an explicit if ( collapse && _grouped_by_distinct ) check in DBIHacks ) + $attrs->{order_by} = $new_order unless $attrs->{collapse}; + } + } + + # inject prefetch-bound selection (if any) + push @{$attrs->{select}}, @prefetch_select; + push @{$attrs->{as}}, @prefetch_as; + + # whether we can get away with the dumbest (possibly DBI-internal) collapser + if ( List::Util::first { $_ =~ /\./ } @{$attrs->{as}} ) { + $attrs->{_related_results_construction} = 1; } # if both page and offset are specified, produce a combined offset @@ -3773,7 +3880,7 @@ sub STORABLE_freeze { # A cursor in progress can't be serialized (and would make little sense anyway) # the parser can be regenerated (and can't be serialized) - delete @{$to_serialize}{qw/cursor _row_parser/}; + 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') { @@ -3810,6 +3917,10 @@ sub throw_exception { } } +1; + +__END__ + # XXX: FIXME: Attributes docs need clearing up =head1 ATTRIBUTES @@ -3859,7 +3970,7 @@ syntax as outlined above. =over 4 -=item Value: \@columns +=item Value: \@columns | \%columns | $column =back @@ -3869,7 +3980,7 @@ 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. @@ -3880,6 +3991,20 @@ is the same as select => [qw/foo baz/], as => [qw/foo bar/] +Like elsewhere, literal SQL or literal values can be included by using a +scalar reference or a literal bind value, and these values will be available +in the result with C (see also +L): + + # equivalent SQL: SELECT 1, 'a string', IF(x,1,2) ... + columns => [ + { + foo => \1, + bar => \q{'a string'}, + baz => \[ '?', 'IF(x,1,2)' ], + } + ] + =head2 +columns =over 4 @@ -3888,10 +4013,10 @@ 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:- $schema->resultset('CD')->search(undef, { '+columns' => ['artist.name'], @@ -3961,14 +4086,6 @@ an explicit list. =back -=head2 +as - -=over 4 - -Indicates additional column names for those added via L. See L. - -=back - =head2 as =over 4 @@ -4011,6 +4128,14 @@ use C instead: You can create your own accessors if required - see L for details. +=head2 +as + +=over 4 + +Indicates additional column names for those added via L. See L. + +=back + =head2 join =over 4 @@ -4074,7 +4199,7 @@ similarly for a third time). For e.g. will return a set of all artists that have both a cd with title 'Down to Earth' and a cd with title 'Popular'. -If you want to fetch related objects from other tables as well, see C +If you want to fetch related objects from other tables as well, see L below. NOTE: An internal join-chain pruner will discard certain joins while @@ -4085,185 +4210,133 @@ below. For more help on using joins with search, see L. -=head2 prefetch +=head2 collapse =over 4 -=item Value: ($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: +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: - 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) - ] - } - ); - -The collapser currently can't identify duplicate tuples for multiple -L relationships and as a -result the second L -relation could contain redundant objects. + my $rs = $schema->resultset('CD')->search({}, { + '+columns' => [ qw/ tracks.title tracks.position / ], + join => 'tracks', + collapse => 1, + }); -=head3 Using L with L +While executing the following query: -L implies a L with the equivalent argument, and is -properly merged with any existing L specification. So the -following: + SELECT me.*, tracks.title, tracks.position + FROM cd me + LEFT JOIN track tracks + ON tracks.cdid = me.cdid - my $rs = $schema->resultset('CD')->search( - {'record_label.name' => 'Music Product Ltd.'}, - { - join => {artist => 'record_label'}, - prefetch => 'artist', - } - ); +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. -... will work, searching on the record label's name, but only -prefetching the C. +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. -=head3 Using L with L / L / L / L +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 constructing the +first object returned by L. -L implies a L/L with the fields of the -prefetched relations. So given: +Setting this attribute on a resultset that does not join any has_many +relations is a no-op. - my $rs = $schema->resultset('CD')->search( - undef, - { - select => ['cd.title'], - as => ['cd_title'], - prefetch => 'artist', - } - ); +For a more in-depth discussion, see L. -The L becomes: C<'cd.title', 'artist.*'> and the L -becomes: C<'cd_title', 'artist.*'>. - -=head3 CAVEATS - -Prefetch does a lot of deep magic. As such, it may not behave exactly -as you might expect. +=head2 prefetch =over 4 -=item * - -Prefetch uses the L to populate the prefetched relationships. This -may or may not be what you want. +=item Value: ($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 @@ -4392,8 +4465,17 @@ or with an in-place function in which case literal SQL is required: =back -Set to 1 to group by all columns. If the resultset already has a group_by -attribute, this setting is ignored and an appropriate warning is issued. +Set to 1 to automatically generate a L clause based on the selection +(including intelligent handling of L contents). Note that the group +criteria calculation takes place over the B selection. This includes +any L, L or L additions in subsequent +L calls, and standalone columns selected via +L (L). A notable exception are the +extra selections specified via L - such selections are explicitly +excluded from group criteria calculations. + +If the final ResultSet also explicitly defines a L attribute, this +setting is ignored and an appropriate warning is issued. =head2 where @@ -4441,6 +4523,131 @@ 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 @@ -4477,7 +4684,7 @@ or to a sensible value based on the "data_type". =item dbic_colname Used to fill in missing sqlt_datatype and sqlt_size attributes (if they are -explicitly specified they are never overriden). Also used by some weird DBDs, +explicitly specified they are never overridden). Also used by some weird DBDs, where the column name should be available at bind_param time (e.g. Oracle). =back @@ -4488,6 +4695,7 @@ supported: [ $name => $val ] === [ { dbic_colname => $name }, $val ] [ \$dt => $val ] === [ { sqlt_datatype => $dt }, $val ] [ undef, $val ] === [ {}, $val ] + $val === [ {}, $val ] =head1 AUTHOR AND CONTRIBUTORS @@ -4497,6 +4705,3 @@ See L and L in You may distribute this code under the same terms as Perl itself. -=cut - -1;