From a24a6624e339611ea5c43e6b19ae5a4b17ea1f71 Mon Sep 17 00:00:00 2001
From: Sven Klemm <pentabarf@gmail.com>
Date: Thu, 12 Jul 2018 13:15:19 +0200
Subject: [PATCH] handle counter overflow and resets in rate

---
 public/app/plugins/datasource/postgres/postgres_query.ts | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/public/app/plugins/datasource/postgres/postgres_query.ts b/public/app/plugins/datasource/postgres/postgres_query.ts
index 9e32736b405..b371af3f1b1 100644
--- a/public/app/plugins/datasource/postgres/postgres_query.ts
+++ b/public/app/plugins/datasource/postgres/postgres_query.ts
@@ -240,7 +240,7 @@ export default class PostgresQuery {
     let special = _.find(column, (g: any) => g.type === 'special');
     if (special) {
       let over = '';
-      if (target.metricColumn) {
+      if (target.metricColumn !== 'None') {
         over = 'PARTITION BY ' + target.metricColumn;
       }
       switch (special.params[0]) {
@@ -249,7 +249,9 @@ export default class PostgresQuery {
           break;
         case 'rate':
           let timeColumn = target.timeColumn;
-          query = '(' + query + ' - lag(' + query + ') OVER (' + over + '))';
+          let curr = query;
+          let prev = 'lag(' + curr + ') OVER (' + over + ')';
+          query = '(CASE WHEN ' + curr + ' >= ' + prev + ' THEN ' + curr + ' - ' + prev + ' ELSE ' + curr + ' END)';
           query += '/extract(epoch from ' + timeColumn + ' - lag(' + timeColumn + ') OVER (' + over + '))';
           break;
       }