fix(Migrations): Introduce url_hash again in case the first migration failed but was marked as done

lib/Migration/Version016002000Date20260218134723.php

@@ -38,17 +38,22 @@ public function postSchemaChange(IOutput $output, Closure $schemaClosure, array
 			->where($setQb->expr()->eq('id', $setQb->createParameter('id')));
 		$i = 1;
 		$this->db->beginTransaction();
-		while ($row = $result->fetch()) {
-			if ($i++ % 1000 === 0) {
-				$this->db->commit();
-				$this->db->beginTransaction();
+		try {
+			while ($row = $result->fetch()) {
+				if ($i++ % 1000 === 0) {
+					$this->db->commit();
+					$this->db->beginTransaction();
+				}
+				$setQb->setParameter('url_hash', hash('xxh128', $row['url']));
+				$setQb->setParameter('id', $row['id']);
+				$setQb->executeStatement();
+				$output->advance();
 			}
-			$setQb->setParameter('url_hash', hash('xxh128', $row['url']));
-			$setQb->setParameter('id', $row['id']);
-			$setQb->executeStatement();
-			$output->advance();
+			$this->db->commit();
+		} catch (\Throwable $e) {
+			$this->db->rollBack();
+			throw $e;
 		}
-		$this->db->commit();
 		$output->finishProgress();
 		$result->closeCursor();
 	}

lib/Migration/Version016002000Date20260717124723.php

@@ -0,0 +1,119 @@
+<?php
+
+/*
+ * Copyright (c) 2020-2024. The Nextcloud Bookmarks contributors.
+ *
+ * This file is licensed under the Affero General Public License version 3 or later. See the COPYING file.
+ */
+
+namespace OCA\Bookmarks\Migration;
+
+use Closure;
+use Doctrine\DBAL\Schema\SchemaException;
+use OCP\DB\ISchemaWrapper;
+use OCP\IDBConnection;
+use OCP\Migration\IOutput;
+
+/**
+ * Recovery migration for instances where the url_hash migration
+ * (Version016002000Date20260201124723) was recorded in oc_migrations but never
+ * actually applied to the schema — e.g. an upgrade that failed in
+ * postSchemaChange on a unique-constraint violation and was then unstuck by a
+ * DB snapshot restore or by manually marking the version as executed.
+ * See https://github.com/nextcloud/bookmarks/issues/2475 and #2374.
+ *
+ * The original migration guards column creation with a `hasColumn` check and,
+ * being recorded as executed, never runs again — so there is otherwise no code
+ * path that will ever create the column. This migration re-establishes the
+ * `url_hash` column and backfills it. The unique index is added by the
+ * following migration (Version016002000Date20260717134723), which must run
+ * only after duplicates have been merged and hashes written here, so that the
+ * index cannot fail on colliding hashes.
+ *
+ * All steps are idempotent: on a healthy instance the column already exists,
+ * there are no NULL hashes to backfill, and this migration is effectively a
+ * no-op.
+ */
+class Version016002000Date20260717124723 extends Version016002000Date20260218124723 {
+	public function __construct(
+		private IDBConnection $db,
+	) {
+		parent::__construct($db);
+	}
+
+	/**
+	 * @throws SchemaException
+	 */
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options) {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+		if ($schema->hasTable('bookmarks')) {
+			$table = $schema->getTable('bookmarks');
+			if (!$table->hasColumn('url_hash')) {
+				$output->info('Recovering missing url_hash column on the bookmarks table');
+				$table->addColumn('url_hash', 'string', [
+					'notnull' => false,
+					'length' => 32,
+				]);
+			}
+		}
+
+		return $schema;
+	}
+
+	public function postSchemaChange(IOutput $output, Closure $schemaClosure, array $options) {
+		// Only do any work if there are bookmarks without a hash. On healthy
+		// instances this short-circuits before the (expensive) dedup scan.
+		$countQb = $this->db->getQueryBuilder();
+		$countQb->select($countQb->func()->count('id'))
+			->from('bookmarks')
+			->where($countQb->expr()->isNull('url_hash'));
+		$result = $countQb->executeQuery();
+		$count = (int)$result->fetchOne();
+		$result->closeCursor();
+
+		if ($count === 0) {
+			return;
+		}
+
+		// Merge per-user duplicate URLs before hashing, otherwise duplicates
+		// would produce colliding (user_id, url_hash) pairs and break the
+		// unique index added by the next migration.
+		$this->deduplicateAll($output);
+
+		$output->info('Hashing URLs of n=' . $count . ' bookmarks');
+		$output->startProgress($count);
+
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('id', 'url')
+			->from('bookmarks')
+			->where($qb->expr()->isNull('url_hash'));
+		$result = $qb->executeQuery();
+
+		$setQb = $this->db->getQueryBuilder();
+		$setQb->update('bookmarks')
+			->set('url_hash', $setQb->createParameter('url_hash'))
+			->where($setQb->expr()->eq('id', $setQb->createParameter('id')));
+
+		$i = 1;
+		$this->db->beginTransaction();
+		try {
+			while ($row = $result->fetch()) {
+				if ($i++ % 1000 === 0) {
+					$this->db->commit();
+					$this->db->beginTransaction();
+				}
+				$setQb->setParameter('url_hash', hash('xxh128', $row['url']));
+				$setQb->setParameter('id', $row['id']);
+				$setQb->executeStatement();
+				$output->advance();
+			}
+			$this->db->commit();
+		} catch (\Throwable $e) {
+			$this->db->rollBack();
+			throw $e;
+		}
+		$output->finishProgress();
+		$result->closeCursor();
+	}
+}

lib/Migration/Version016002000Date20260717134723.php

@@ -0,0 +1,50 @@
+<?php
+
+/*
+ * Copyright (c) 2020-2024. The Nextcloud Bookmarks contributors.
+ *
+ * This file is licensed under the Affero General Public License version 3 or later. See the COPYING file.
+ */
+
+namespace OCA\Bookmarks\Migration;
+
+use Closure;
+use Doctrine\DBAL\Schema\SchemaException;
+use OCP\DB\ISchemaWrapper;
+use OCP\IDBConnection;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+/**
+ * Recovery migration (part 2) for instances that lost the url_hash unique
+ * index. See Version016002000Date20260717124723 and
+ * https://github.com/nextcloud/bookmarks/issues/2475.
+ *
+ * Runs after the column has been (re-)created and hashes have been backfilled
+ * and de-duplicated, so the unique index cannot fail on colliding hashes.
+ * Idempotent: on a healthy instance the index already exists and this is a
+ * no-op.
+ */
+class Version016002000Date20260717134723 extends SimpleMigrationStep {
+	public function __construct(
+		private IDBConnection $db,
+	) {
+	}
+
+	/**
+	 * @throws SchemaException
+	 */
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options) {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+		if ($schema->hasTable('bookmarks')) {
+			$table = $schema->getTable('bookmarks');
+			if ($table->hasColumn('url_hash') && !$table->hasIndex('bookmarks_uniq_url')) {
+				$output->info('Recovering missing bookmarks_uniq_url unique index');
+				$table->addUniqueIndex(['user_id', 'url_hash'], 'bookmarks_uniq_url');
+			}
+		}
+
+		return $schema;
+	}
+}