Active-only UNIQUE indexes on user.email + user.username (TIGER-274)

CHANGELOG.md

@@ -6,6 +6,19 @@ All notable changes to **Tiger Core** (`webtigers/tiger-core`). Format follows
 
 ## [Unreleased]
 
+## [1.19.0] — 2026-10-01
+
+### Changed
+
+- **Active-only UNIQUE indexes on `user.email` + `user.username` — soft-delete now frees the value
+  (TIGER-274).** A plain `UNIQUE(col)` spans soft-deleted (`deleted=1`) rows, so soft-deleting a user
+  never freed their email/username and a re-signup with that address collided on the index. Migration
+  `0053` moves each unique index onto a generated `<col>_active = IF(deleted=0, col, NULL)` column —
+  MySQL/MariaDB allow multiple NULLs in a unique index, so soft-deleted rows drop out and the value is
+  reusable, while live rows stay unique. The real `email`/`username` columns are untouched and the
+  finders already filter `deleted=0`, so there is no behavioral change for live rows. This is the
+  platform-wide convention for every unique + soft-deletable column (TIGER-274).
+
 ## [1.18.1] — 2026-09-27
 
 ### Fixed

library/Tiger/Version.php

@@ -9,5 +9,5 @@
 class Tiger_Version
 {
     /** Current Tiger Core version. Keep in lockstep with the git tag cut for a release. */
-    const VERSION = '1.18.1';
+    const VERSION = '1.19.0';
 }

migrations/0053_active_only_user_unique.php

@@ -0,0 +1,33 @@
+<?php
+// SPDX-License-Identifier: BSD-3-Clause
+// Copyright (c) 2026 WebTigers. Tiger™ and WebTigers™ are trademarks of WebTigers.
+/**
+ * Migration 0053 — active-only UNIQUE indexes on `user.email` + `user.username` (TIGER-274).
+ *
+ * A plain UNIQUE spans soft-deleted rows too (ARCHITECTURE §7a: "a deleted row still holds its unique
+ * value"), so soft-delete never frees an email/username — a re-signup with a deleted account's address
+ * collides on the index instead of gracefully reusing it. Index a generated
+ * `<col>_active = IF(deleted=0, col, NULL)` instead: MySQL/MariaDB allow multiple NULLs in a unique
+ * index, so deleted rows drop out (NULL) and free the value, while live rows stay unique. The real
+ * `email`/`username` columns are untouched — `Tiger_Model_User::findByEmail`/finders already filter
+ * `deleted=0`, so no application code changes. This is the convention for every unique + soft-deletable
+ * column platform-wide (see TIGER-274).
+ */
+return [
+    'up' => [
+        "ALTER TABLE `user` DROP INDEX `uq_user_email`",
+        "ALTER TABLE `user` ADD COLUMN `email_active` VARCHAR(191) GENERATED ALWAYS AS (IF(`deleted`=0, `email`, NULL)) VIRTUAL",
+        "ALTER TABLE `user` ADD UNIQUE KEY `uq_user_email_active` (`email_active`)",
+        "ALTER TABLE `user` DROP INDEX `uq_user_username`",
+        "ALTER TABLE `user` ADD COLUMN `username_active` VARCHAR(64) GENERATED ALWAYS AS (IF(`deleted`=0, `username`, NULL)) VIRTUAL",
+        "ALTER TABLE `user` ADD UNIQUE KEY `uq_user_username_active` (`username_active`)",
+    ],
+    'down' => [
+        "ALTER TABLE `user` DROP INDEX `uq_user_email_active`",
+        "ALTER TABLE `user` DROP COLUMN `email_active`",
+        "ALTER TABLE `user` ADD UNIQUE KEY `uq_user_email` (`email`)",
+        "ALTER TABLE `user` DROP INDEX `uq_user_username_active`",
+        "ALTER TABLE `user` DROP COLUMN `username_active`",
+        "ALTER TABLE `user` ADD UNIQUE KEY `uq_user_username` (`username`)",
+    ],
+];