fix: explicitly forbid offset and limit in partitioned queries

as there is no proper way to implement this that isn't very slow

Signed-off-by: Robin Appelman <robin@icewind.nl>

lib/private/DB/QueryBuilder/Partitioned/PartitionedQueryBuilder.php

@@ -99,6 +99,7 @@
  * 7. Update, delete and insert statements aren't allowed to contain cross-partition joins.
  * 8. Queries that "GROUP BY" a column from the joined partition are not allowed.
  * 9. Any `join` call needs to be made before any `where` call.
+ * 10. Queries that join cross-partition cannot use "LIMIT" or "OFFSET" in queries.
  *
  * [1]: A set of tables which can't be queried together with the rest of the tables, such as when sharding is used.
  */
@@ -113,6 +114,8 @@ class PartitionedQueryBuilder extends ShardedQueryBuilder {
 	private ?PartitionSplit $mainPartition = null;
 	private bool $hasPositionalParameter = false;
 	private QuoteHelper $quoteHelper;
+	private ?int $limit = null;
+	private ?int $offset = null;
 
 	public function __construct(
 		IQueryBuilder          $builder,
@@ -397,6 +400,20 @@ public function delete($delete = null, $alias = null) {
 		return parent::delete($delete, $alias);
 	}
 
+	public function setMaxResults($maxResults) {
+		if ($maxResults > 0) {
+			$this->limit = (int)$maxResults;
+		}
+		return parent::setMaxResults($maxResults);
+	}
+
+	public function setFirstResult($firstResult) {
+		if ($firstResult > 0) {
+			$this->offset = (int)$firstResult;
+		}
+		return parent::setFirstResult($firstResult);
+	}
+
 	public function executeQuery(?IDBConnection $connection = null): IResult {
 		$this->applySelects();
 		if ($this->splitQueries && $this->hasPositionalParameter) {
@@ -405,6 +422,14 @@ public function executeQuery(?IDBConnection $connection = null): IResult {
 		foreach ($this->splitQueries as $split) {
 			$split->query->setParameters($this->getParameters(), $this->getParameterTypes());
 		}
+		if (count($this->splitQueries) > 0) {
+			if (is_int($this->limit)) {
+				throw new InvalidPartitionedQueryException("Limit is not allowed in partitioned queries");
+			}
+			if (is_int($this->offset)) {
+				throw new InvalidPartitionedQueryException("Offset is not allowed in partitioned queries");
+			}
+		}
 
 		$s = parent::getSQL();
 		$result = parent::executeQuery($connection);