person: add unique index on table relationship to avoid duplicate fromperson_id/toperson_id pairs

src/Bundle/ChillPersonBundle/migrations/Version20220425000000.php

@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * Chill is a software for social workers
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Chill\Migrations\Person;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Add constraint with a index on chill_person_relationships.
+ */
+final class Version20220425000000 extends AbstractMigration
+{
+    public function down(Schema $schema): void
+    {
+        $this->addSql('DROP INDEX IDX_RELATIONSHIPS000');
+    }
+
+    public function getDescription(): string
+    {
+        return 'Add constraint with a index on chill_person_relationships.';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('CREATE UNIQUE INDEX IDX_RELATIONSHIPS000 ON chill_person_relationships (least(fromperson_id, toperson_id), greatest(fromperson_id, toperson_id))');
+    }
+}
+