From: Loic Dachary <loic@dachary.org>
Date: Fri, 27 Sep 2013 17:09:23 +0000 (+0200)
Subject: common: document ghobject sort order rationale
X-Git-Tag: v0.71~40^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=refs%2Fpull%2F652%2Fhead;p=ceph.git

common: document ghobject sort order rationale

Intuition differs regarding the sort order of the ghobject shard and
generation. Document the rationale for the chosen sort order.

Reviewed-by: Samuel Just <sam.just@inktank.com>
Reviewed-by: David Zafman <david.zafman@inktank.com>
Signed-off-by: Loic Dachary <loic@dachary.org>
---

diff --git a/src/common/hobject.h b/src/common/hobject.h
index 46fc67b893a4..82eecf3bfc7b 100644
--- a/src/common/hobject.h
+++ b/src/common/hobject.h
@@ -288,8 +288,12 @@ namespace __gnu_cxx {
 
 ostream& operator<<(ostream& out, const ghobject_t& o);
 
-WRITE_EQ_OPERATORS_3(ghobject_t, hobj, generation, shard_id)
-// sort ghobject_t's by <hobj, generation, shard_id>
+WRITE_EQ_OPERATORS_3(ghobject_t, hobj, shard_id, generation)
+// sort ghobject_t's by <hobj, shard_id, generation> 
+// 
+// Two objects which differ by generation are more related than
+// two objects of the same generation which differ by shard.
+// 
 WRITE_CMP_OPERATORS_3(ghobject_t,
 		      hobj,
 		      shard_id,