12 my $schema = DBICTest->init_schema();
13 my $sdebug = $schema->storage->debug;
15 # once the following TODO is complete, remove the 2 warning tests immediately
16 # after the TODO block
17 # (the TODO block itself contains tests ensuring that the warns are removed)
19 local $TODO = 'Prefetch of multiple has_many rels at the same level (currently warn to protect the clueless git)';
22 my $cd_rs = $schema->resultset('CD')->search ({ 'me.title' => 'Forkful of bees' });
23 my $pr_cd_rs = $cd_rs->search ({}, {
24 prefetch => [qw/tracks tags/],
27 my $tracks_rs = $cd_rs->first->tracks;
28 my $tracks_count = $tracks_rs->count;
30 my ($pr_tracks_rs, $pr_tracks_count);
33 $schema->storage->debugcb(sub { $queries++ });
34 $schema->storage->debug(1);
38 local $SIG{__WARN__} = sub { $o_mm_warn = shift };
39 $pr_tracks_rs = $pr_cd_rs->first->tracks;
41 $pr_tracks_count = $pr_tracks_rs->count;
43 ok(! $o_mm_warn, 'no warning on attempt to prefetch several same level has_many\'s (1 -> M + M)');
45 is($queries, 1, 'prefetch one->(has_many,has_many) ran exactly 1 query');
46 $schema->storage->debugcb (undef);
47 $schema->storage->debug ($sdebug);
49 is($pr_tracks_count, $tracks_count, 'equal count of prefetched relations over several same level has_many\'s (1 -> M + M)');
50 is ($pr_tracks_rs->all, $tracks_rs->all, 'equal amount of objects returned with and without prefetch over several same level has_many\'s (1 -> M + M)');
53 my $note_rs = $schema->resultset('LinerNotes')->search ({ notes => 'Buy Whiskey!' });
54 my $pr_note_rs = $note_rs->search ({}, {
56 cd => [qw/tracks tags/]
60 my $tags_rs = $note_rs->first->cd->tags;
61 my $tags_count = $tags_rs->count;
63 my ($pr_tags_rs, $pr_tags_count);
66 $schema->storage->debugcb(sub { $queries++ });
67 $schema->storage->debug(1);
71 local $SIG{__WARN__} = sub { $m_o_mm_warn = shift };
72 $pr_tags_rs = $pr_note_rs->first->cd->tags;
74 $pr_tags_count = $pr_tags_rs->count;
76 ok(! $m_o_mm_warn, 'no warning on attempt to prefetch several same level has_many\'s (M -> 1 -> M + M)');
78 is($queries, 1, 'prefetch one->(has_many,has_many) ran exactly 1 query');
79 $schema->storage->debugcb (undef);
80 $schema->storage->debug ($sdebug);
82 is($pr_tags_count, $tags_count, 'equal count of prefetched relations over several same level has_many\'s (M -> 1 -> M + M)');
83 is($pr_tags_rs->all, $tags_rs->all, 'equal amount of objects with and without prefetch over several same level has_many\'s (M -> 1 -> M + M)');
86 # remove this closure once the TODO above is working
88 my $warn_re = qr/will explode the number of row objects retrievable via/;
91 local $SIG{__WARN__} = sub { $_[0] =~ $warn_re ? push @w, @_ : warn @_ };
93 my $rs = $schema->resultset('CD')->search ({ 'me.title' => 'Forkful of bees' }, { prefetch => [qw/tracks tags/] });
96 is (@w, 1, 'warning on attempt prefetching several same level has_manys (1 -> M + M)');
98 my $rs2 = $schema->resultset('LinerNotes')->search ({ notes => 'Buy Whiskey!' }, { prefetch => { cd => [qw/tags tracks/] } });
100 @dummy = $rs2->first;
101 is (@w, 1, 'warning on attempt prefetching several same level has_manys (M -> 1 -> M + M)');
105 # Illustration purposes only
114 my $cd = $schema->resultset ('CD')->create ({
118 tags => [ map { { tag => "bad tag $_" } } (1 .. 3) ],
120 { title => 'bad track 1', cd_single => {
122 title => 'bad_single',
125 map { { title => "bad track $_" } } (2 .. 3),
129 my $rs = $schema->resultset ('CD')->search (
130 { 'me.cdid' => $cd->id },
131 { prefetch => [ 'tags', { tracks => 'cd_single' } ], result_class => 'Inf::Dump' },
135 my $query = ${$rs->as_query}->[0];
136 my ($cols) = ( $query =~ /SELECT (.+) FROM/);
137 my $tb = Text::Table->new (map { $_ => \ ' | ' } (split /,\s*/, $cols) );
140 while (my @stuff = $c->next) {
141 $tb->add (map { defined $_ ? $_ : 'NULL' } (@stuff) );
156 The solution is to rewrite ResultSet->_collapse_result() and
157 ResultSource->resolve_prefetch() to focus on the final results from the collapse
158 of the data. Right now, the code doesn't treat the columns from the various
159 tables as grouped entities. While there is a concept of hierarchy (so that
160 prefetching down relationships does work as expected), there is no idea of what
161 the final product should look like and how the various columns in the row would
162 play together. So, the actual prefetch datastructure from the search would be
163 very useful in working through this problem. We already have access to the PKs
164 and sundry for those. So, when collapsing the search result, we know we are
165 looking for 1 cd object. We also know we're looking for tracks and tags records
166 -independently- of each other. So, we can grab the data for tracks and data for
167 tags separately, uniqueing on the PK as appropriate. Then, when we're done with
168 the given cd object's datastream, we know we're good. This should work for all
169 the various scenarios.
171 My reccommendation is the row's data is preprocessed first, breaking it up into
172 the data for each of the component tables. (This could be done in the single
173 table case, too, but probably isn't necessary.) So, starting with something
183 it is massaged to look something like:
185 t1 => { col1 => 1, col2 => 2 },
186 t2 => { col1 => 3, col2 => 4 },
187 t3 => { col1 => 5, col2 => 6 },
189 At this point, find the stuff that's different is easy enough to do and slotting
190 things into the right spot is, likewise, pretty straightforward. Instead of
191 storing things in a AoH, store them in a HoH keyed on the PKs of the the table,
192 then convert to an AoH after all collapsing is done.
194 This implies that the collapse attribute can probably disappear or, at the
195 least, be turned into a boolean (which is how it's used in every other place).