Split the two discussion_id -> post_id migrations into 4 total

migrations/2023_07_08_000000_rename_polls_discussion_id_column.php

@@ -12,16 +12,15 @@
 use Illuminate\Database\Schema\Blueprint;
 use Illuminate\Database\Schema\Builder;
 
+// Split 1/2 of 2023_07_08_000000_rename_polls_discussion_id_column.php
 return [
     'up' => function (Builder $schema) {
         $schema->table('polls', function (Blueprint $table) {
             $table->dropForeign(['discussion_id']);
-            $table->renameColumn('discussion_id', 'post_id');
         });
     },
     'down' => function (Builder $schema) {
         $schema->table('polls', function (Blueprint $table) {
-            $table->renameColumn('post_id', 'discussion_id');
             $table->foreign('discussion_id')->references('id')->on('discussions')->onDelete('cascade');
         });
     },

migrations/2023_07_08_000000_rename_polls_discussion_id_column_1.php

@@ -0,0 +1,32 @@
+<?php
+
+/*
+ * This file is part of fof/polls.
+ *
+ * Copyright (c) FriendsOfFlarum.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Schema\Builder;
+
+// Split 2/2 of 2023_07_08_000000_rename_polls_discussion_id_column.php
+return [
+    'up' => function (Builder $schema) {
+        // Do not run this migration if the column was already renamed before the split
+        if ($schema->hasColumn('polls', 'post_id')) {
+            return;
+        }
+
+        $schema->table('polls', function (Blueprint $table) {
+            $table->renameColumn('discussion_id', 'post_id');
+        });
+    },
+    'down' => function (Builder $schema) {
+        $schema->table('polls', function (Blueprint $table) {
+            $table->renameColumn('post_id', 'discussion_id');
+        });
+    },
+];

migrations/2023_07_08_000001_update_polls_discussion_relation_to_first_post.php

@@ -13,6 +13,7 @@
 use Illuminate\Database\Schema\Blueprint;
 use Illuminate\Database\Schema\Builder;
 
+// Split 1/2 of 2023_07_08_000001_update_polls_discussion_relation_to_first_post.php
 return [
     'up' => function (Builder $schema) {
         $db = $schema->getConnection();
@@ -61,10 +62,6 @@
 
             $deletingPolls->delete();
         });
-
-        $schema->table('polls', function (Blueprint $table) {
-            $table->foreign('post_id')->references('id')->on('posts')->onDelete('cascade');
-        });
     },
     'down' => function (Builder $schema) {
         $db = $schema->getConnection();
@@ -82,9 +79,5 @@
                 ->join('posts', 'polls.post_id', '=', 'posts.id')
                 ->update(['polls.post_id' => $db->raw("{$prefix}posts.discussion_id")]);
         });
-
-        $schema->table('polls', function (Blueprint $table) {
-            $table->dropForeign(['post_id']);
-        });
     },
 ];

migrations/2023_07_08_000002_add_polls_post_id_foreign.php

@@ -0,0 +1,39 @@
+<?php
+
+/*
+ * This file is part of fof/polls.
+ *
+ * Copyright (c) FriendsOfFlarum.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Illuminate\Database\Query\JoinClause;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Schema\Builder;
+use Illuminate\Support\Arr;
+
+// Split 2/2 of 2023_07_08_000001_update_polls_discussion_relation_to_first_post.php
+return [
+    'up' => function (Builder $schema) {
+        // Do not run this migration if the foreign key was already added before the split
+        $db = $schema->getConnection();
+        $foreignKeys = $db->getDoctrineSchemaManager()->listTableForeignKeys("{$db->getTablePrefix()}polls");
+
+        foreach ($foreignKeys as $foreignKey) {
+            if (in_array('post_id', $foreignKey->getLocalColumns())) {
+                return;
+            }
+        }
+
+        $schema->table('polls', function (Blueprint $table) {
+            $table->foreign('post_id')->references('id')->on('posts')->onDelete('cascade');
+        });
+    },
+    'down' => function (Builder $schema) {
+        $schema->table('polls', function (Blueprint $table) {
+            $table->dropForeign(['post_id']);
+        });
+    },
+];