From e53e82faf3cb7c53da8618f3c6c672a7e7b3584a Mon Sep 17 00:00:00 2001
From: Shlee <github@shl.ee>
Date: Sat, 29 Aug 2026 22:52:55 +0930
Subject: [PATCH] Update 2025_07_31_164635_change_hashtags_collation.php

---
 ...07_31_164635_change_hashtags_collation.php | 68 +++++++++++++++----
 1 file changed, 54 insertions(+), 14 deletions(-)

diff --git a/database/migrations/2025_07_31_164635_change_hashtags_collation.php b/database/migrations/2025_07_31_164635_change_hashtags_collation.php
index bd621ccfa..6a1f965e1 100644
--- a/database/migrations/2025_07_31_164635_change_hashtags_collation.php
+++ b/database/migrations/2025_07_31_164635_change_hashtags_collation.php
@@ -1,23 +1,36 @@
 <?php
 
 use Illuminate\Database\Migrations\Migration;
-use Illuminate\Database\Schema\Blueprint;
-use Illuminate\Support\Facades\Schema;
+use Illuminate\Support\Facades\DB;
 
 return new class extends Migration
 {
+    /**
+     * The collation that correctly differentiates characters outside the
+     * Basic Multilingual Plane (codepoints >= 0x10000). The historic default
+     * of utf8mb4_unicode_ci treats all such characters as equal, which causes
+     * distinct hashtags (e.g. Shavian vs cuneiform of the same length) to
+     * collide on the unique name/slug indexes.
+     */
+    private const TARGET_COLLATION = 'utf8mb4_unicode_520_ci';
+
+    /**
+     * The collation to restore on rollback (the previous project default).
+     */
+    private const PREVIOUS_COLLATION = 'utf8mb4_unicode_ci';
+
+    /**
+     * Column definitions to keep intact while altering the collation. Both are
+     * VARCHAR(255) NOT NULL with unique indexes; MODIFY preserves the index.
+     */
+    private const COLUMNS = ['name', 'slug'];
+
     /**
      * Run the migrations.
      */
     public function up(): void
     {
-        if (config('database.default') === 'pgsql')
-            return;
-
-        Schema::table('hashtags', function (Blueprint $table) {
-            $table->string('name')->collation('utf8mb4_unicode_520_ci')->change();
-            $table->string('slug')->collation('utf8mb4_unicode_520_ci')->change();
-        });
+        $this->setCollation(self::TARGET_COLLATION);
     }
 
     /**
@@ -25,12 +38,39 @@ return new class extends Migration
      */
     public function down(): void
     {
-        if (config('database.default') === 'pgsql')
+        $this->setCollation(self::PREVIOUS_COLLATION);
+    }
+
+    /**
+     * Apply the given collation to the hashtags name and slug columns.
+     *
+     * Laravel's fluent ->change() does not reliably emit a collation-only
+     * change on MySQL/MariaDB, so issue an explicit MODIFY per column.
+     */
+    private function setCollation(string $collation): void
+    {
+        if (! $this->isMysql()) {
             return;
+        }
 
-        Schema::table('hashtags', function (Blueprint $table) {
-            $table->string('name')->change();
-            $table->string('slug')->change();
-        });
+        foreach (self::COLUMNS as $column) {
+            DB::statement(
+                'ALTER TABLE `hashtags` MODIFY `'.$column.'` '.
+                'VARCHAR(255) CHARACTER SET utf8mb4 COLLATE '.$collation.' NOT NULL'
+            );
+        }
+    }
+
+    /**
+     * This migration only applies to MySQL/MariaDB. Postgres compares
+     * hashtags with ILIKE (no collation quirk) and other drivers (e.g. the
+     * sqlite test database) do not support these collations.
+     *
+     * Note: Laravel 11+ reports MariaDB as the distinct "mariadb" driver, so
+     * both must be matched here.
+     */
+    private function isMysql(): bool
+    {
+        return in_array(DB::connection()->getDriverName(), ['mysql', 'mariadb'], true);
     }
 };