From: Peter Rabbitson <ribasushi@cpan.org>
Date: Sun, 20 Apr 2008 18:44:16 +0000 (+0000)
Subject: Split prefetch related tests from 76joins.t
X-Git-Tag: v0.08240~482
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=96e7f9ec94671f14005e5b2a159c7a555fde21d9;p=dbsrgits%2FDBIx-Class.git

Split prefetch related tests from 76joins.t
---

diff --git a/t/76joins.t b/t/76joins.t
index 101d71f..dba7c00 100644
--- a/t/76joins.t
+++ b/t/76joins.t
@@ -16,7 +16,7 @@ BEGIN {
     eval "use DBD::SQLite";
     plan $@
         ? ( skip_all => 'needs DBD::SQLite for testing' )
-        : ( tests => 64 );
+        : ( tests => 16 );
 }
 
 # figure out if we've got a version of sqlite that is older than 3.2.6, in
@@ -157,315 +157,3 @@ cmp_ok( $rs->count, '==', 1, "Single record in resultset");
 
 is($rs->first->name, 'We Are Goth', 'Correct record returned');
 
-# bug in 0.07000 caused attr (join/prefetch) to be modifed by search
-# so we check the search & attr arrays are not modified
-my $search = { 'artist.name' => 'Caterwauler McCrae' };
-my $attr = { prefetch => [ qw/artist liner_notes/ ],
-             order_by => 'me.cdid' };
-my $search_str = Dumper($search);
-my $attr_str = Dumper($attr);
-
-$rs = $schema->resultset("CD")->search($search, $attr);
-
-is(Dumper($search), $search_str, 'Search hash untouched after search()');
-is(Dumper($attr), $attr_str, 'Attribute hash untouched after search()');
-cmp_ok($rs + 0, '==', 3, 'Correct number of records returned');
-
-my $queries = 0;
-$schema->storage->debugcb(sub { $queries++; });
-$schema->storage->debug(1);
-
-my @cd = $rs->all;
-
-is($cd[0]->title, 'Spoonful of bees', 'First record returned ok');
-
-ok(!defined $cd[0]->liner_notes, 'No prefetch for NULL LEFT join');
-
-is($cd[1]->{_relationship_data}{liner_notes}->notes, 'Buy Whiskey!', 'Prefetch for present LEFT JOIN');
-
-is(ref $cd[1]->liner_notes, 'DBICTest::LinerNotes', 'Prefetch returns correct class');
-
-is($cd[2]->{_inflated_column}{artist}->name, 'Caterwauler McCrae', 'Prefetch on parent object ok');
-
-is($queries, 1, 'prefetch ran only 1 select statement');
-
-$schema->storage->debug($orig_debug);
-$schema->storage->debugobj->callback(undef);
-
-# test for partial prefetch via columns attr
-my $cd = $schema->resultset('CD')->find(1,
-    {
-      columns => [qw/title artist.name/], 
-      join => { 'artist' => {} }
-    }
-);
-ok(eval { $cd->artist->name eq 'Caterwauler McCrae' }, 'single related column prefetched');
-
-# start test for nested prefetch SELECT count
-$queries = 0;
-$schema->storage->debugcb(sub { $queries++ });
-$schema->storage->debug(1);
-
-$rs = $schema->resultset('Tag')->search(
-  {},
-  {
-    prefetch => { cd => 'artist' }
-  }
-);
-
-my $tag = $rs->first;
-
-is( $tag->cd->title, 'Spoonful of bees', 'step 1 ok for nested prefetch' );
-
-is( $tag->cd->artist->name, 'Caterwauler McCrae', 'step 2 ok for nested prefetch');
-
-# count the SELECTs
-#$selects++ if /SELECT(?!.*WHERE 1=0.*)/;
-is($queries, 1, 'nested prefetch ran exactly 1 select statement (excluding column_info)');
-
-$queries = 0;
-
-is($tag->search_related('cd')->search_related('artist')->first->name,
-   'Caterwauler McCrae',
-   'chained belongs_to->belongs_to search_related ok');
-
-is($queries, 0, 'chained search_related after belontgs_to->belongs_to prefetch ran no queries');
-
-$queries = 0;
-
-$cd = $schema->resultset('CD')->find(1, { prefetch => 'artist' });
-
-is($cd->{_inflated_column}{artist}->name, 'Caterwauler McCrae', 'artist prefetched correctly on find');
-
-is($queries, 1, 'find with prefetch ran exactly 1 select statement (excluding column_info)');
-
-$queries = 0;
-
-$schema->storage->debugcb(sub { $queries++; });
-
-$cd = $schema->resultset('CD')->find(1, { prefetch => { cd_to_producer => 'producer' } });
-
-is($cd->producers->first->name, 'Matt S Trout', 'many_to_many accessor ok');
-
-is($queries, 1, 'many_to_many accessor with nested prefetch ran exactly 1 query');
-
-$queries = 0;
-
-my $producers = $cd->search_related('cd_to_producer')->search_related('producer');
-
-is($producers->first->name, 'Matt S Trout', 'chained many_to_many search_related ok');
-
-is($queries, 0, 'chained search_related after many_to_many prefetch ran no queries');
-
-$schema->storage->debug($orig_debug);
-$schema->storage->debugobj->callback(undef);
-
-$rs = $schema->resultset('Tag')->search(
-  {},
-  {
-    join => { cd => 'artist' },
-    prefetch => { cd => 'artist' }
-  }
-);
-
-cmp_ok( $rs->count, '>=', 0, 'nested prefetch does not duplicate joins' );
-
-my ($artist) = $schema->resultset("Artist")->search({ 'cds.year' => 2001 },
-                 { order_by => 'artistid DESC', join => 'cds' });
-
-is($artist->name, 'Random Boy Band', "Join search by object ok");
-
-my @cds = $schema->resultset("CD")->search({ 'liner_notes.notes' => 'Buy Merch!' },
-                               { join => 'liner_notes' });
-
-cmp_ok(scalar @cds, '==', 1, "Single CD retrieved via might_have");
-
-is($cds[0]->title, "Generic Manufactured Singles", "Correct CD retrieved");
-
-my @artists = $schema->resultset("Artist")->search({ 'tags.tag' => 'Shiny' },
-                                       { join => { 'cds' => 'tags' } });
-
-cmp_ok( @artists, '==', 2, "two-join search ok" );
-
-$rs = $schema->resultset("CD")->search(
-  {},
-  { group_by => [qw/ title me.cdid /] }
-);
-
-SKIP: {
-    skip "SQLite < 3.2.6 doesn't understand COUNT(DISTINCT())", 1
-        if $is_broken_sqlite;
-    cmp_ok( $rs->count, '==', 5, "count() ok after group_by on main pk" );
-}
-
-cmp_ok( scalar $rs->all, '==', 5, "all() returns same count as count() after group_by on main pk" );
-
-$rs = $schema->resultset("CD")->search(
-  {},
-  { join => [qw/ artist /], group_by => [qw/ artist.name /] }
-);
-
-SKIP: {
-    skip "SQLite < 3.2.6 doesn't understand COUNT(DISTINCT())", 1
-        if $is_broken_sqlite;
-    cmp_ok( $rs->count, '==', 3, "count() ok after group_by on related column" );
-}
-
-$rs = $schema->resultset("Artist")->search(
-  {},
-      { join => [qw/ cds /], group_by => [qw/ me.name /], having =>{ 'MAX(cds.cdid)'=> \'< 5' } }
-);
-
-cmp_ok( $rs->all, '==', 2, "results ok after group_by on related column with a having" );
-
-$rs = $rs->search( undef, {  having =>{ 'count(*)'=> \'> 2' }});
-
-cmp_ok( $rs->all, '==', 1, "count() ok after group_by on related column with a having" );
-
-$rs = $schema->resultset("Artist")->search(
-        { 'cds.title' => 'Spoonful of bees',
-          'cds_2.title' => 'Forkful of bees' },
-        { join => [ 'cds', 'cds' ] });
-
-SKIP: {
-    skip "SQLite < 3.2.6 doesn't understand COUNT(DISTINCT())", 1
-        if $is_broken_sqlite;
-    cmp_ok($rs->count, '==', 1, "single artist returned from multi-join");
-}
-
-is($rs->next->name, 'Caterwauler McCrae', "Correct artist returned");
-
-$cd = $schema->resultset('Artist')->first->create_related('cds',
-    {
-    title   => 'Unproduced Single',
-    year    => 2007
-});
-
-my $left_join = $schema->resultset('CD')->search(
-    { 'me.cdid' => $cd->cdid },
-    { prefetch => { cd_to_producer => 'producer' } }
-);
-
-cmp_ok($left_join, '==', 1, 'prefetch with no join record present');
-
-$queries = 0;
-$schema->storage->debugcb(sub { $queries++ });
-$schema->storage->debug(1);
-
-my $tree_like =
-     $schema->resultset('TreeLike')->find(4,
-       { join     => { parent => { parent => 'parent' } },
-         prefetch => { parent => { parent => 'parent' } } });
-
-is($tree_like->name, 'quux', 'Bottom of tree ok');
-$tree_like = $tree_like->parent;
-is($tree_like->name, 'baz', 'First level up ok');
-$tree_like = $tree_like->parent;
-is($tree_like->name, 'bar', 'Second level up ok');
-$tree_like = $tree_like->parent;
-is($tree_like->name, 'foo', 'Third level up ok');
-
-$schema->storage->debug($orig_debug);
-$schema->storage->debugobj->callback(undef);
-
-cmp_ok($queries, '==', 1, 'Only one query run');
-
-$tree_like = $schema->resultset('TreeLike')->search({'me.id' => 1});
-$tree_like = $tree_like->search_related('children')->search_related('children')->search_related('children')->first;
-is($tree_like->name, 'quux', 'Tree search_related ok');
-
-$tree_like = $schema->resultset('TreeLike')->search_related('children',
-    { 'children.id' => 2, 'children_2.id' => 3 },
-    { prefetch => { children => 'children' } }
-  )->first;
-is(eval { $tree_like->children->first->children->first->name }, 'quux',
-   'Tree search_related with prefetch ok');
-
-$tree_like = eval { $schema->resultset('TreeLike')->search(
-    { 'children.id' => 2, 'children_2.id' => 5 }, 
-    { join => [qw/children children/] }
-  )->search_related('children', { 'children_4.id' => 6 }, { prefetch => 'children' }
-  )->first->children->first; };
-is(eval { $tree_like->name }, 'fong', 'Tree with multiple has_many joins ok');
-
-# test that collapsed joins don't get a _2 appended to the alias
-
-my $sql = '';
-$schema->storage->debugcb(sub { $sql = $_[1] });
-$schema->storage->debug(1);
-
-eval {
-  my $row = $schema->resultset('Artist')->search_related('cds', undef, {
-    join => 'tracks',
-    prefetch => 'tracks',
-  })->search_related('tracks')->first;
-};
-
-like( $sql, qr/^SELECT tracks_2\.trackid/, "join not collapsed for search_related" );
-
-$schema->storage->debug($orig_debug);
-$schema->storage->debugobj->callback(undef);
-
-$rs = $schema->resultset('Artist');
-$rs->create({ artistid => 4, name => 'Unknown singer-songwriter' });
-$rs->create({ artistid => 5, name => 'Emo 4ever' });
-@artists = $rs->search(undef, { prefetch => 'cds', order_by => 'artistid' });
-is(scalar @artists, 5, 'has_many prefetch with adjacent empty rows ok');
-
-# -------------
-#
-# Tests for multilevel has_many prefetch
-
-# artist resultsets - with and without prefetch
-my $art_rs = $schema->resultset('Artist');
-my $art_rs_pr = $art_rs->search(
-    {},
-    {
-        join     => [ { cds => ['tracks'] } ],
-        prefetch => [ { cds => ['tracks'] } ],
-        cache    => 1 # last test needs this
-    }
-);
-
-# This test does the same operation twice - once on a
-# set of items fetched from the db with no prefetch of has_many rels
-# The second prefetches 2 levels of has_many
-# We check things are the same by comparing the name or title
-# we build everything into a hash structure and compare the one
-# from each rs to see what differs
-
-sub make_hash_struc {
-    my $rs = shift;
-
-    my $struc = {};
-    foreach my $art ( $rs->all ) {
-        foreach my $cd ( $art->cds ) {
-            foreach my $track ( $cd->tracks ) {
-                $struc->{ $art->name }{ $cd->title }{ $track->title }++;
-            }
-        }
-    }
-    return $struc;
-}
-
-$queries = 0;
-$schema->storage->debugcb(sub { $queries++ });
-$schema->storage->debug(1);
-
-my $prefetch_result = make_hash_struc($art_rs_pr);
-
-is($queries, 1, 'nested prefetch across has_many->has_many ran exactly 1 query');
-
-my $nonpre_result   = make_hash_struc($art_rs);
-
-is_deeply( $prefetch_result, $nonpre_result,
-    'Compare 2 level prefetch result to non-prefetch result' );
-
-$queries = 0;
-
-is($art_rs_pr->search_related('cds')->search_related('tracks')->first->title,
-   'Fowlin',
-   'chained has_many->has_many search_related ok'
-  );
-
-is($queries, 0, 'chained search_related after has_many->has_many prefetch ran no queries');
diff --git a/t/77prefetch.t b/t/77prefetch.t
new file mode 100644
index 0000000..2276964
--- /dev/null
+++ b/t/77prefetch.t
@@ -0,0 +1,345 @@
+use strict;
+use warnings;  
+
+use Test::More;
+use lib qw(t/lib);
+use DBICTest;
+use Data::Dumper;
+
+my $schema = DBICTest->init_schema();
+
+my $orig_debug = $schema->storage->debug;
+
+use IO::File;
+
+BEGIN {
+    eval "use DBD::SQLite";
+    plan $@
+        ? ( skip_all => 'needs DBD::SQLite for testing' )
+        : ( tests => 48 );
+}
+
+# figure out if we've got a version of sqlite that is older than 3.2.6, in
+# which case COUNT(DISTINCT()) doesn't work
+my $is_broken_sqlite = 0;
+my ($sqlite_major_ver,$sqlite_minor_ver,$sqlite_patch_ver) =
+    split /\./, $schema->storage->dbh->get_info(18);
+if( $schema->storage->dbh->get_info(17) eq 'SQLite' &&
+    ( ($sqlite_major_ver < 3) ||
+      ($sqlite_major_ver == 3 && $sqlite_minor_ver < 2) ||
+      ($sqlite_major_ver == 3 && $sqlite_minor_ver == 2 && $sqlite_patch_ver < 6) ) ) {
+    $is_broken_sqlite = 1;
+}
+
+# bug in 0.07000 caused attr (join/prefetch) to be modifed by search
+# so we check the search & attr arrays are not modified
+my $search = { 'artist.name' => 'Caterwauler McCrae' };
+my $attr = { prefetch => [ qw/artist liner_notes/ ],
+             order_by => 'me.cdid' };
+my $search_str = Dumper($search);
+my $attr_str = Dumper($attr);
+
+my $rs = $schema->resultset("CD")->search($search, $attr);
+
+is(Dumper($search), $search_str, 'Search hash untouched after search()');
+is(Dumper($attr), $attr_str, 'Attribute hash untouched after search()');
+cmp_ok($rs + 0, '==', 3, 'Correct number of records returned');
+
+my $queries = 0;
+$schema->storage->debugcb(sub { $queries++; });
+$schema->storage->debug(1);
+
+my @cd = $rs->all;
+
+is($cd[0]->title, 'Spoonful of bees', 'First record returned ok');
+
+ok(!defined $cd[0]->liner_notes, 'No prefetch for NULL LEFT join');
+
+is($cd[1]->{_relationship_data}{liner_notes}->notes, 'Buy Whiskey!', 'Prefetch for present LEFT JOIN');
+
+is(ref $cd[1]->liner_notes, 'DBICTest::LinerNotes', 'Prefetch returns correct class');
+
+is($cd[2]->{_inflated_column}{artist}->name, 'Caterwauler McCrae', 'Prefetch on parent object ok');
+
+is($queries, 1, 'prefetch ran only 1 select statement');
+
+$schema->storage->debug($orig_debug);
+$schema->storage->debugobj->callback(undef);
+
+# test for partial prefetch via columns attr
+my $cd = $schema->resultset('CD')->find(1,
+    {
+      columns => [qw/title artist.name/], 
+      join => { 'artist' => {} }
+    }
+);
+ok(eval { $cd->artist->name eq 'Caterwauler McCrae' }, 'single related column prefetched');
+
+# start test for nested prefetch SELECT count
+$queries = 0;
+$schema->storage->debugcb(sub { $queries++ });
+$schema->storage->debug(1);
+
+$rs = $schema->resultset('Tag')->search(
+  {},
+  {
+    prefetch => { cd => 'artist' }
+  }
+);
+
+my $tag = $rs->first;
+
+is( $tag->cd->title, 'Spoonful of bees', 'step 1 ok for nested prefetch' );
+
+is( $tag->cd->artist->name, 'Caterwauler McCrae', 'step 2 ok for nested prefetch');
+
+# count the SELECTs
+#$selects++ if /SELECT(?!.*WHERE 1=0.*)/;
+is($queries, 1, 'nested prefetch ran exactly 1 select statement (excluding column_info)');
+
+$queries = 0;
+
+is($tag->search_related('cd')->search_related('artist')->first->name,
+   'Caterwauler McCrae',
+   'chained belongs_to->belongs_to search_related ok');
+
+is($queries, 0, 'chained search_related after belontgs_to->belongs_to prefetch ran no queries');
+
+$queries = 0;
+
+$cd = $schema->resultset('CD')->find(1, { prefetch => 'artist' });
+
+is($cd->{_inflated_column}{artist}->name, 'Caterwauler McCrae', 'artist prefetched correctly on find');
+
+is($queries, 1, 'find with prefetch ran exactly 1 select statement (excluding column_info)');
+
+$queries = 0;
+
+$schema->storage->debugcb(sub { $queries++; });
+
+$cd = $schema->resultset('CD')->find(1, { prefetch => { cd_to_producer => 'producer' } });
+
+is($cd->producers->first->name, 'Matt S Trout', 'many_to_many accessor ok');
+
+is($queries, 1, 'many_to_many accessor with nested prefetch ran exactly 1 query');
+
+$queries = 0;
+
+my $producers = $cd->search_related('cd_to_producer')->search_related('producer');
+
+is($producers->first->name, 'Matt S Trout', 'chained many_to_many search_related ok');
+
+is($queries, 0, 'chained search_related after many_to_many prefetch ran no queries');
+
+$schema->storage->debug($orig_debug);
+$schema->storage->debugobj->callback(undef);
+
+$rs = $schema->resultset('Tag')->search(
+  {},
+  {
+    join => { cd => 'artist' },
+    prefetch => { cd => 'artist' }
+  }
+);
+
+cmp_ok( $rs->count, '>=', 0, 'nested prefetch does not duplicate joins' );
+
+my ($artist) = $schema->resultset("Artist")->search({ 'cds.year' => 2001 },
+                 { order_by => 'artistid DESC', join => 'cds' });
+
+is($artist->name, 'Random Boy Band', "Join search by object ok");
+
+my @cds = $schema->resultset("CD")->search({ 'liner_notes.notes' => 'Buy Merch!' },
+                               { join => 'liner_notes' });
+
+cmp_ok(scalar @cds, '==', 1, "Single CD retrieved via might_have");
+
+is($cds[0]->title, "Generic Manufactured Singles", "Correct CD retrieved");
+
+my @artists = $schema->resultset("Artist")->search({ 'tags.tag' => 'Shiny' },
+                                       { join => { 'cds' => 'tags' } });
+
+cmp_ok( @artists, '==', 2, "two-join search ok" );
+
+$rs = $schema->resultset("CD")->search(
+  {},
+  { group_by => [qw/ title me.cdid /] }
+);
+
+SKIP: {
+    skip "SQLite < 3.2.6 doesn't understand COUNT(DISTINCT())", 1
+        if $is_broken_sqlite;
+    cmp_ok( $rs->count, '==', 5, "count() ok after group_by on main pk" );
+}
+
+cmp_ok( scalar $rs->all, '==', 5, "all() returns same count as count() after group_by on main pk" );
+
+$rs = $schema->resultset("CD")->search(
+  {},
+  { join => [qw/ artist /], group_by => [qw/ artist.name /] }
+);
+
+SKIP: {
+    skip "SQLite < 3.2.6 doesn't understand COUNT(DISTINCT())", 1
+        if $is_broken_sqlite;
+    cmp_ok( $rs->count, '==', 3, "count() ok after group_by on related column" );
+}
+
+$rs = $schema->resultset("Artist")->search(
+  {},
+      { join => [qw/ cds /], group_by => [qw/ me.name /], having =>{ 'MAX(cds.cdid)'=> \'< 5' } }
+);
+
+cmp_ok( $rs->all, '==', 2, "results ok after group_by on related column with a having" );
+
+$rs = $rs->search( undef, {  having =>{ 'count(*)'=> \'> 2' }});
+
+cmp_ok( $rs->all, '==', 1, "count() ok after group_by on related column with a having" );
+
+$rs = $schema->resultset("Artist")->search(
+        { 'cds.title' => 'Spoonful of bees',
+          'cds_2.title' => 'Forkful of bees' },
+        { join => [ 'cds', 'cds' ] });
+
+SKIP: {
+    skip "SQLite < 3.2.6 doesn't understand COUNT(DISTINCT())", 1
+        if $is_broken_sqlite;
+    cmp_ok($rs->count, '==', 1, "single artist returned from multi-join");
+}
+
+is($rs->next->name, 'Caterwauler McCrae', "Correct artist returned");
+
+$cd = $schema->resultset('Artist')->first->create_related('cds',
+    {
+    title   => 'Unproduced Single',
+    year    => 2007
+});
+
+my $left_join = $schema->resultset('CD')->search(
+    { 'me.cdid' => $cd->cdid },
+    { prefetch => { cd_to_producer => 'producer' } }
+);
+
+cmp_ok($left_join, '==', 1, 'prefetch with no join record present');
+
+$queries = 0;
+$schema->storage->debugcb(sub { $queries++ });
+$schema->storage->debug(1);
+
+my $tree_like =
+     $schema->resultset('TreeLike')->find(4,
+       { join     => { parent => { parent => 'parent' } },
+         prefetch => { parent => { parent => 'parent' } } });
+
+is($tree_like->name, 'quux', 'Bottom of tree ok');
+$tree_like = $tree_like->parent;
+is($tree_like->name, 'baz', 'First level up ok');
+$tree_like = $tree_like->parent;
+is($tree_like->name, 'bar', 'Second level up ok');
+$tree_like = $tree_like->parent;
+is($tree_like->name, 'foo', 'Third level up ok');
+
+$schema->storage->debug($orig_debug);
+$schema->storage->debugobj->callback(undef);
+
+cmp_ok($queries, '==', 1, 'Only one query run');
+
+$tree_like = $schema->resultset('TreeLike')->search({'me.id' => 1});
+$tree_like = $tree_like->search_related('children')->search_related('children')->search_related('children')->first;
+is($tree_like->name, 'quux', 'Tree search_related ok');
+
+$tree_like = $schema->resultset('TreeLike')->search_related('children',
+    { 'children.id' => 2, 'children_2.id' => 3 },
+    { prefetch => { children => 'children' } }
+  )->first;
+is(eval { $tree_like->children->first->children->first->name }, 'quux',
+   'Tree search_related with prefetch ok');
+
+$tree_like = eval { $schema->resultset('TreeLike')->search(
+    { 'children.id' => 2, 'children_2.id' => 5 }, 
+    { join => [qw/children children/] }
+  )->search_related('children', { 'children_4.id' => 6 }, { prefetch => 'children' }
+  )->first->children->first; };
+is(eval { $tree_like->name }, 'fong', 'Tree with multiple has_many joins ok');
+
+# test that collapsed joins don't get a _2 appended to the alias
+
+my $sql = '';
+$schema->storage->debugcb(sub { $sql = $_[1] });
+$schema->storage->debug(1);
+
+eval {
+  my $row = $schema->resultset('Artist')->search_related('cds', undef, {
+    join => 'tracks',
+    prefetch => 'tracks',
+  })->search_related('tracks')->first;
+};
+
+like( $sql, qr/^SELECT tracks_2\.trackid/, "join not collapsed for search_related" );
+
+$schema->storage->debug($orig_debug);
+$schema->storage->debugobj->callback(undef);
+
+$rs = $schema->resultset('Artist');
+$rs->create({ artistid => 4, name => 'Unknown singer-songwriter' });
+$rs->create({ artistid => 5, name => 'Emo 4ever' });
+@artists = $rs->search(undef, { prefetch => 'cds', order_by => 'artistid' });
+is(scalar @artists, 5, 'has_many prefetch with adjacent empty rows ok');
+
+# -------------
+#
+# Tests for multilevel has_many prefetch
+
+# artist resultsets - with and without prefetch
+my $art_rs = $schema->resultset('Artist');
+my $art_rs_pr = $art_rs->search(
+    {},
+    {
+        join     => [ { cds => ['tracks'] } ],
+        prefetch => [ { cds => ['tracks'] } ],
+        cache    => 1 # last test needs this
+    }
+);
+
+# This test does the same operation twice - once on a
+# set of items fetched from the db with no prefetch of has_many rels
+# The second prefetches 2 levels of has_many
+# We check things are the same by comparing the name or title
+# we build everything into a hash structure and compare the one
+# from each rs to see what differs
+
+sub make_hash_struc {
+    my $rs = shift;
+
+    my $struc = {};
+    foreach my $art ( $rs->all ) {
+        foreach my $cd ( $art->cds ) {
+            foreach my $track ( $cd->tracks ) {
+                $struc->{ $art->name }{ $cd->title }{ $track->title }++;
+            }
+        }
+    }
+    return $struc;
+}
+
+$queries = 0;
+$schema->storage->debugcb(sub { $queries++ });
+$schema->storage->debug(1);
+
+my $prefetch_result = make_hash_struc($art_rs_pr);
+
+is($queries, 1, 'nested prefetch across has_many->has_many ran exactly 1 query');
+
+my $nonpre_result   = make_hash_struc($art_rs);
+
+is_deeply( $prefetch_result, $nonpre_result,
+    'Compare 2 level prefetch result to non-prefetch result' );
+
+$queries = 0;
+
+is($art_rs_pr->search_related('cds')->search_related('tracks')->first->title,
+   'Fowlin',
+   'chained has_many->has_many search_related ok'
+  );
+
+is($queries, 0, 'chained search_related after has_many->has_many prefetch ran no queries');