10 my $schema = DBICTest->init_schema();
12 my $orig_debug = $schema->storage->debug;
17 eval "use DBD::SQLite";
19 ? ( skip_all => 'needs DBD::SQLite for testing' )
24 # once the following TODO is complete, remove the 2 warning tests immediately
25 # after the TODO block
26 # (the TODO block itself contains tests ensuring that the warns are removed)
28 local $TODO = 'Prefetch of multiple has_many rels at the same level (currently warn to protect the clueless git)';
31 my $cd_rs = $schema->resultset('CD')->search ({ 'me.title' => 'Forkful of bees' });
32 my $pr_cd_rs = $cd_rs->search ({}, {
33 prefetch => [qw/tracks tags/],
36 my $tracks_rs = $cd_rs->first->tracks;
37 my $tracks_count = $tracks_rs->count;
39 my ($pr_tracks_rs, $pr_tracks_count);
42 $schema->storage->debugcb(sub { $queries++ });
43 $schema->storage->debug(1);
47 local $SIG{__WARN__} = sub { $o_mm_warn = shift };
48 $pr_tracks_rs = $pr_cd_rs->first->tracks;
50 $pr_tracks_count = $pr_tracks_rs->count;
52 ok(! $o_mm_warn, 'no warning on attempt to prefetch several same level has_many\'s (1 -> M + M)');
54 is($queries, 1, 'prefetch one->(has_many,has_many) ran exactly 1 query');
55 is($pr_tracks_count, $tracks_count, 'equal count of prefetched relations over several same level has_many\'s (1 -> M + M)');
57 for ($pr_tracks_rs, $tracks_rs) {
58 $_->result_class ('DBIx::Class::ResultClass::HashRefInflator');
61 is_deeply ([$pr_tracks_rs->all], [$tracks_rs->all], 'same structure returned with and without prefetch over several same level has_many\'s (1 -> M + M)');
64 my $note_rs = $schema->resultset('LinerNotes')->search ({ notes => 'Buy Whiskey!' });
65 my $pr_note_rs = $note_rs->search ({}, {
67 cd => [qw/tags tracks/]
71 my $tags_rs = $note_rs->first->cd->tags;
72 my $tags_count = $tags_rs->count;
74 my ($pr_tags_rs, $pr_tags_count);
77 $schema->storage->debugcb(sub { $queries++ });
78 $schema->storage->debug(1);
82 local $SIG{__WARN__} = sub { $m_o_mm_warn = shift };
83 $pr_tags_rs = $pr_note_rs->first->cd->tags;
85 $pr_tags_count = $pr_tags_rs->count;
87 ok(! $m_o_mm_warn, 'no warning on attempt to prefetch several same level has_many\'s (M -> 1 -> M + M)');
89 is($queries, 1, 'prefetch one->(has_many,has_many) ran exactly 1 query');
91 is($pr_tags_count, $tags_count, 'equal count of prefetched relations over several same level has_many\'s (M -> 1 -> M + M)');
93 for ($pr_tags_rs, $tags_rs) {
94 $_->result_class ('DBIx::Class::ResultClass::HashRefInflator');
97 is_deeply ([$pr_tags_rs->all], [$tags_rs->all], 'same structure returned with and without prefetch over several same level has_many\'s (M -> 1 -> M + M)');
100 # remove this closure once the TODO above is working
103 local $SIG{__WARN__} = sub { $w = shift };
105 my $rs = $schema->resultset('CD')->search ({ 'me.title' => 'Forkful of bees' }, { prefetch => [qw/tracks tags/] });
106 for (qw/all count next first/) {
108 my @stuff = $rs->search()->$_;
109 like ($w, qr/will currently disrupt both the functionality of .rs->count\(\), and the amount of objects retrievable via .rs->next\(\)/,
110 "warning on ->$_ attempt prefetching several same level has_manys (1 -> M + M)");
112 my $rs2 = $schema->resultset('LinerNotes')->search ({ notes => 'Buy Whiskey!' }, { prefetch => { cd => [qw/tags tracks/] } });
113 for (qw/all count next first/) {
115 my @stuff = $rs2->search()->$_;
116 like ($w, qr/will currently disrupt both the functionality of .rs->count\(\), and the amount of objects retrievable via .rs->next\(\)/,
117 "warning on ->$_ attempt prefetching several same level has_manys (M -> 1 -> M + M)");
122 # Illustration purposes only
131 my $cd = $schema->resultset ('CD')->create ({
135 tags => [ map { { tag => "bad tag $_" } } (1 .. 3) ],
137 { title => 'bad track 1', cd_single => {
139 title => 'bad_single',
142 map { { title => "bad track $_" } } (2 .. 3),
146 my $rs = $schema->resultset ('CD')->search (
147 { 'me.cdid' => $cd->id },
148 { prefetch => [ 'tags', { tracks => 'cd_single' } ], result_class => 'Inf::Dump' },
152 my $query = ${$rs->as_query}->[0];
153 my ($cols) = ( $query =~ /SELECT (.+) FROM/);
154 my $tb = Text::Table->new (map { $_ => \ ' | ' } (split /,\s*/, $cols) );
157 while (my @stuff = $c->next) {
158 $tb->add (map { defined $_ ? $_ : 'NULL' } (@stuff) );
172 The solution is to rewrite ResultSet->_collapse_result() and
173 ResultSource->resolve_prefetch() to focus on the final results from the collapse
174 of the data. Right now, the code doesn't treat the columns from the various
175 tables as grouped entities. While there is a concept of hierarchy (so that
176 prefetching down relationships does work as expected), there is no idea of what
177 the final product should look like and how the various columns in the row would
178 play together. So, the actual prefetch datastructure from the search would be
179 very useful in working through this problem. We already have access to the PKs
180 and sundry for those. So, when collapsing the search result, we know we are
181 looking for 1 cd object. We also know we're looking for tracks and tags records
182 -independently- of each other. So, we can grab the data for tracks and data for
183 tags separately, uniqueing on the PK as appropriate. Then, when we're done with
184 the given cd object's datastream, we know we're good. This should work for all
185 the various scenarios.
187 My reccommendation is the row's data is preprocessed first, breaking it up into
188 the data for each of the component tables. (This could be done in the single
189 table case, too, but probably isn't necessary.) So, starting with something
199 it is massaged to look something like:
201 t1 => { col1 => 1, col2 => 2 },
202 t2 => { col1 => 3, col2 => 4 },
203 t3 => { col1 => 5, col2 => 6 },
205 At this point, find the stuff that's different is easy enough to do and slotting
206 things into the right spot is, likewise, pretty straightforward.
208 This implies that the collapse attribute can probably disappear or, at the
209 least, be turned into a boolean (which is how it's used in every other place).