From 7c0c6b1167319d814157b8cd4c9c7605eef162d3 Mon Sep 17 00:00:00 2001
From: Oliver Lloyd <oliver_lloyd@hotmail.com>
Date: Wed, 11 Jul 2012 00:44:16 +0200
Subject: [PATCH] Added an example for an aggregate key as this was not clear.

---
 source/reference/aggregation.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/source/reference/aggregation.txt b/source/reference/aggregation.txt
index c106ec9aa9e..3c2bdc98568 100644
--- a/source/reference/aggregation.txt
+++ b/source/reference/aggregation.txt
@@ -423,6 +423,10 @@ The current pipeline operators are:
    a single field from the documents in the pipeline, a previously computed
    value, or an aggregate key made up from several incoming fields.
 
+   .. note::
+
+      An aggregate key takes the format: ``{myKeyName: { author:true, myOtherField:true , YetAnotherField:true}}``.
+
    Every group expression must specify an ``_id`` field.
    You may specify the ``_id`` field as a dotted
    field path reference, a document with multiple fields enclosed in