perf: index telemetry timestamps

Index timestamp lookups used by telemetry statistics and result listing.

results/telemetry_db.php

@@ -138,6 +138,10 @@ function getPdo($returnErrorMessage = false)
                 `log`       longtext
                 );
             ');
+            // Every query that is not a lookup by id orders or filters by
+            // timestamp, and without this the table is scanned in full each
+            // time. The other schemas declare the same index.
+            $pdo->exec('CREATE INDEX IF NOT EXISTS `speedtest_users_timestamp` ON `speedtest_users` (`timestamp`);');
 
             return $pdo;
         }

results/telemetry_mssql.sql

@@ -33,4 +33,10 @@ GO
 ALTER TABLE [dbo].[speedtest_users] ADD  CONSTRAINT [DF_speedtest_users_timestamp]  DEFAULT (getdate()) FOR [timestamp]
 GO
 
+CREATE NONCLUSTERED INDEX [speedtest_users_timestamp] ON [dbo].[speedtest_users]
+(
+	[timestamp] ASC
+) ON [PRIMARY]
+GO
+
 

results/telemetry_mysql.sql

@@ -42,7 +42,8 @@ CREATE TABLE `speedtest_users` (
 -- Indexes for table `speedtest_users`
 --
 ALTER TABLE `speedtest_users`
-  ADD PRIMARY KEY (`id`);
+  ADD PRIMARY KEY (`id`),
+  ADD KEY `speedtest_users_timestamp` (`timestamp`);
 
 --
 -- AUTO_INCREMENT for dumped tables

results/telemetry_postgresql.sql

@@ -107,6 +107,13 @@ ALTER TABLE ONLY speedtest_users
     ADD CONSTRAINT speedtest_users_pkey PRIMARY KEY (id);
 
 
+--
+-- Name: speedtest_users_timestamp; Type: INDEX; Schema: public; Owner: speedtest
+--
+
+CREATE INDEX speedtest_users_timestamp ON speedtest_users USING btree ("timestamp");
+
+
 --
 -- PostgreSQL database dump complete
 --