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diff --git a/lib/private/DB/QueryBuilder/Sharded/InvalidShardedQueryException.php b/lib/private/DB/QueryBuilder/Sharded/InvalidShardedQueryException.php
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+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+namespace OC\DB\QueryBuilder\Sharded;
+
+/**
+ * Queries on sharded table has the following limitations:
+ *
+ * 1. Either the shard key (e.g. "storage") or primary key (e.g. "fileid") must be mentioned in the query.
+ *    Or the query must be explicitly marked as running across all shards.
+ *
+ *    For queries where it isn't possible to set one of these keys in the query normally, you can set it using `hintShardKey`
+ *
+ * 2. Insert statements must always explicitly set the shard key
+ * 3. A query on a sharded table is not allowed to join on the same table
+ * 4. Right joins are not allowed on sharded tables
+ * 5. Updating the shard key where the new shard key maps to a different shard is not allowed
+ *
+ *    Moving rows to a different shard needs to be implemented manually. `CrossShardMoveHelper` provides
+ *    some tools to help make this easier.
+ */
+class InvalidShardedQueryException extends \Exception {
+
+}