From f889ac1140c20fbe506d3918dfc4b4127d351170 Mon Sep 17 00:00:00 2001
From: Philip O'Toole <philip@influxdb.com>
Date: Thu, 12 Nov 2015 18:52:58 -0800
Subject: [PATCH] If no points to count, count is 0

Fix issue #4701.
---
 cmd/influxd/run/server_test.go | 5 +++++
 tsdb/functions.go              | 5 +----
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/cmd/influxd/run/server_test.go b/cmd/influxd/run/server_test.go
index 3f633019af..68669c320d 100644
--- a/cmd/influxd/run/server_test.go
+++ b/cmd/influxd/run/server_test.go
@@ -1146,6 +1146,11 @@ func TestServer_Query_Count(t *testing.T) {
 			command: fmt.Sprintf(`SELECT count(value) FROM db0.rp0.cpu WHERE time >= '%s'`, hour_ago.Format(time.RFC3339Nano)),
 			exp:     fmt.Sprintf(`{"results":[{"series":[{"name":"cpu","columns":["time","count"],"values":[["%s",1]]}]}]}`, hour_ago.Format(time.RFC3339Nano)),
 		},
+		&Query{
+			name:    "selecting count(value) with filter that excludes all results should return 0",
+			command: fmt.Sprintf(`SELECT count(value) FROM db0.rp0.cpu WHERE value=100 AND time >= '%s'`, hour_ago.Format(time.RFC3339Nano)),
+			exp:     fmt.Sprintf(`{"results":[{"series":[{"name":"cpu","columns":["time","count"],"values":[["%s",0]]}]}]}`, hour_ago.Format(time.RFC3339Nano)),
+		},
 		&Query{
 			name:    "selecting count(*) should error",
 			command: `SELECT count(*) FROM db0.rp0.cpu`,
diff --git a/tsdb/functions.go b/tsdb/functions.go
index 61da27957e..f10b0cb468 100644
--- a/tsdb/functions.go
+++ b/tsdb/functions.go
@@ -250,10 +250,7 @@ func MapCount(input *MapInput) interface{} {
 	for range input.Items {
 		n++
 	}
-	if n > 0 {
-		return n
-	}
-	return nil
+	return n
 }
 
 type InterfaceValues []interface{}