Add migration to remove duplicated keys

Due to old/corrupted data, it can be problematic to restore a backup

server/initializers/constants.ts

@@ -24,7 +24,7 @@ import { CONFIG, registerConfigChangedHandler } from './config'
 
 // ---------------------------------------------------------------------------
 
-const LAST_MIGRATION_VERSION = 635
+const LAST_MIGRATION_VERSION = 640
 
 // ---------------------------------------------------------------------------
 

server/initializers/migrations/0640-unique-keys.ts

@@ -0,0 +1,39 @@
+import * as Sequelize from 'sequelize'
+
+async function up (utils: {
+  transaction: Sequelize.Transaction
+  queryInterface: Sequelize.QueryInterface
+  sequelize: Sequelize.Sequelize
+  db: any
+}): Promise<void> {
+  {
+    await utils.sequelize.query(
+      'DELETE FROM "actor" v1 USING (SELECT MIN(id) as id, "preferredUsername", "serverId" FROM "actor" ' +
+      'GROUP BY "preferredUsername", "serverId" HAVING COUNT(*) > 1 AND "serverId" IS NOT NULL) v2 ' +
+      'WHERE v1."preferredUsername" = v2."preferredUsername" AND v1."serverId" = v2."serverId" AND v1.id <> v2.id'
+    )
+  }
+
+  {
+    await utils.sequelize.query(
+      'DELETE FROM "actor" v1 USING (SELECT MIN(id) as id, "url" FROM "actor" GROUP BY "url" HAVING COUNT(*) > 1) v2 ' +
+      'WHERE v1."url" = v2."url" AND v1.id <> v2.id'
+    )
+  }
+
+  {
+    await utils.sequelize.query(
+      'DELETE FROM "tag" v1 USING (SELECT MIN(id) as id, "name" FROM "tag" GROUP BY "name" HAVING COUNT(*) > 1) v2 ' +
+      'WHERE v1."name" = v2."name" AND v1.id <> v2.id'
+    )
+  }
+}
+
+function down (options) {
+  throw new Error('Not implemented.')
+}
+
+export {
+  up,
+  down
+}