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Signed-off-by: Carl Schwan <carl@carlschwan.eu>

lib/Migration/Version23000Date2022022912000001.php

@@ -38,26 +38,25 @@ class Version23000Date2022022912000001 extends SimpleMigrationStep {
 	protected $connection;
 
 	public function __construct(IDBConnection $connection) {
-		$this->connection = \OC::$server->get(IDBConnection::class);
+		$this->connection = $connection;
 	}
 
 	public function preSchemaChange(IOutput $output, Closure $schemaClosure, array $options) {
 		$query = $this->connection->getQueryBuilder();
 
-		$query->select($query->func()->count('*', 'num_entry'), 'user_id')
-			->from('notification_tracker');
+		// delete all but one entries for each user_id
+		$query->select($query->func()->max('id', 'newest_entry'), 'user_id')
+			->from('notification_tracker')
+			->groupBy('user_id');
 
 		$result = $query->executeQuery();
-		while ($row = $result->fetch()) {
-			$userId = $row['user_id'];
-			$entriesToDelete = (int)$row['num_entry'] - 1;
-			if ($entriesToDelete > 0) {
-				$delete = $this->connection->getQueryBuilder();
-				$delete->delete('notification_tracker')
-					->where($delete->expr()->eq('user_id', $delete->createNamedParameter($userId)))
-					->setMaxResults($entriesToDelete);
-
-			}
+		$rows = $result->fetchAll();
+		foreach ($rows as $row)
+			$delete = $this->connection->getQueryBuilder();
+			$delete->delete('notification_tracker')
+				->where($delete->expr()->eq('user_id', $delete->createNamedParameter($row['user_id'])))
+				->andWhere($delete->expr()->neq('id', $delete->createNamedParameter($row['newest_entry'])));
+			$delete->execute();
 		}
 	}