Fixed #8486: Add index for asset serial number

database/migrations/2021_06_07_155421_add_serial_number_indexes.php

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