From: Peter Rabbitson <ribasushi@cpan.org>
Date: Sat, 9 Mar 2013 18:41:41 +0000 (+0100)
Subject: There is no point of ordering the insides of a complex prefetch without a limit
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=4df1400e9a42e3e19f143151de2c8ba5865cb553;p=dbsrgits%2FDBIx-Class-Historic.git

There is no point of ordering the insides of a complex prefetch without a limit
---

diff --git a/Changes b/Changes
index 995dc25..24dd469 100644
--- a/Changes
+++ b/Changes
@@ -10,6 +10,8 @@ Revision history for DBIx::Class
           invalid relationship graph
         - Warn in case of iterative collapse being upgraded to an eager
           cursor slurp
+        - No longer order the insides of a complex prefetch subquery,
+          unless required to satisfy a limit
 
     * Fixes
         - Properly consider unselected order_by criteria during complex
diff --git a/lib/DBIx/Class/Storage/DBIHacks.pm b/lib/DBIx/Class/Storage/DBIHacks.pm
index e5a0d83..75a8fb2 100644
--- a/lib/DBIx/Class/Storage/DBIHacks.pm
+++ b/lib/DBIx/Class/Storage/DBIHacks.pm
@@ -85,8 +85,12 @@ sub _adjust_select_args_for_complex_prefetch {
   my $inner_attrs = { %$attrs };
   delete $inner_attrs->{$_} for qw/for collapse _prefetch_selector_range select as/;
 
-  # if the user did not request it, there is no point using it inside
-  delete $inner_attrs->{order_by} if delete $inner_attrs->{_order_is_artificial};
+  # there is no point of ordering the insides if there is no limit
+  delete $inner_attrs->{order_by} if (
+    delete $inner_attrs->{_order_is_artificial}
+      or
+    ! $inner_attrs->{rows}
+  );
 
   # generate the inner/outer select lists
   # for inside we consider only stuff *not* brought in by the prefetch
diff --git a/t/prefetch/grouped.t b/t/prefetch/grouped.t
index 40ac923..f5d56bb 100644
--- a/t/prefetch/grouped.t
+++ b/t/prefetch/grouped.t
@@ -224,7 +224,6 @@ for ($cd_rs->all) {
           SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
             FROM cd me
           GROUP BY me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
-          ORDER BY cdid
         ) me
         LEFT JOIN tags tags ON tags.cd = me.cdid
       ORDER BY cdid