From 58bd49ee95dc055d65939b32c139c63d881c1710 Mon Sep 17 00:00:00 2001
From: Fengqian Gao <fengqian.gao@intel.com>
Date: Wed, 19 Feb 2014 15:45:10 +0800
Subject: [PATCH] Add comments for _build_paginate_query

Add comments for _build_paginate_query which will called
_recurse_sort_keys. It will generate the query criteria
recursively if multiple sort keys passed in.

Change-Id: I102308fc1a57f1ba8bd96e64badedbcf60840c28
---
 ceilometer/storage/impl_mongodb.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/ceilometer/storage/impl_mongodb.py b/ceilometer/storage/impl_mongodb.py
index 62fff58b4..b94dc5f2b 100644
--- a/ceilometer/storage/impl_mongodb.py
+++ b/ceilometer/storage/impl_mongodb.py
@@ -547,6 +547,14 @@ class Connection(base.Connection):
             sort_criteria_list = []
 
             for i in range(len(sort_keys)):
+                #NOTE(fengqian): Generate the query criteria recursively.
+                #sort_keys=[k1, k2, k3], maker_value=[v1, v2, v3]
+                #sort_flags = ['$lt', '$gt', 'lt'].
+                #The query criteria should be
+                #{'k3': {'$lt': 'v3'}, 'k2': {'eq': 'v2'}, 'k1': {'eq': 'v1'}},
+                #{'k2': {'$gt': 'v2'}, 'k1': {'eq': 'v1'}},
+                #{'k1': {'$lt': 'v1'}} with 'OR' operation.
+                #Each recurse will generate one items of three.
                 sort_criteria_list.append(cls._recurse_sort_keys(
                                           sort_keys[:(len(sort_keys) - i)],
                                           marker, _op))