From e6e0df6aff4cefffd75568f8d2db12a15dacbdf0 Mon Sep 17 00:00:00 2001
From: epriestley <git@epriestley.com>
Date: Mon, 4 May 2015 10:04:27 -0700
Subject: [PATCH] Compute average costs more correctly in Multimeter

Summary: Ref T6930. We were dividing total cost by number of samples, but should more accurately divide it by the sum of the sample rates. This produces a more meaningful number.

Test Plan: Saw a more meaningful number in the UI.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6930

Differential Revision: https://secure.phabricator.com/D12655
---
 .../multimeter/controller/MultimeterSampleController.php   | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/applications/multimeter/controller/MultimeterSampleController.php b/src/applications/multimeter/controller/MultimeterSampleController.php
index 62a459f75b..06dc13e81b 100644
--- a/src/applications/multimeter/controller/MultimeterSampleController.php
+++ b/src/applications/multimeter/controller/MultimeterSampleController.php
@@ -56,7 +56,10 @@ final class MultimeterSampleController extends MultimeterController {
 
     $data = queryfx_all(
       $conn,
-      'SELECT *, count(*) N, SUM(sampleRate * resourceCost) as totalCost
+      'SELECT *,
+          count(*) AS N,
+          SUM(sampleRate * resourceCost) AS totalCost,
+          SUM(sampleRate * resourceCost) / SUM(sampleRate) AS averageCost
         FROM %T
         WHERE %Q
         GROUP BY %Q
@@ -177,7 +180,7 @@ final class MultimeterSampleController extends MultimeterController {
         MultimeterEvent::formatResourceCost(
           $viewer,
           $row['eventType'],
-          $row['totalCost'] / $row['N']),
+          $row['averageCost']),
         MultimeterEvent::formatResourceCost(
           $viewer,
           $row['eventType'],