Add index on starred entries

Fixes #4079

Signed-off-by: Olivier Mehani <shtrom@ssji.net>

app/DoctrineMigrations/Version20190806131006.php

@@ -0,0 +1,22 @@
+<?php declare(strict_types=1);
+
+namespace Application\Migrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Auto-generated Migration: Please modify to your needs!
+ */
+final class Version20190806131006 extends AbstractMigration
+{
+    public function up(Schema $schema) : void
+    {
+        $this->addSql('CREATE INDEX user_starred ON wallabag_entry (user_id, is_starred, starred_at)');
+    }
+
+    public function down(Schema $schema) : void
+    {
+        $this->addSql('DROP INDEX user_starred ON `wallabag_entry`');
+    }
+}