Add missing index for device_perf (#11974)

Makes the latency page load faster in case of a large device_perf table

database/migrations/2020_07_29_143221_add_device_perf_index.php

@@ -0,0 +1,32 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class AddDevicePerfIndex extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::table('device_perf', function (Blueprint $table) {
+            $table->index(['device_id', 'timestamp']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::table('device_perf', function (Blueprint $table) {
+            $table->dropIndex(['device_id', 'timestamp']);
+        });
+    }
+}

misc/db_schema.yaml

@@ -605,6 +605,7 @@ device_perf:
   Indexes:
     PRIMARY: { Name: PRIMARY, Columns: [id], Unique: true, Type: BTREE }
     device_perf_device_id_index: { Name: device_perf_device_id_index, Columns: [device_id], Unique: false, Type: BTREE }
+    device_perf_device_id_timestamp_index: { Name: device_perf_device_id_timestamp_index, Columns: [device_id, timestamp], Unique: false, Type: BTREE }
 device_relationships:
   Columns:
     - { Field: parent_device_id, Type: 'int unsigned', 'Null': false, Extra: '', Default: '0' }