fix: Chunk in-queries to 1000 items

Signed-off-by: Julius Härtl <jus@bitgrid.net>

lib/Db/DeckMapper.php

@@ -23,6 +23,7 @@
 
 namespace OCA\Deck\Db;
 
+use Generator;
 use OCP\AppFramework\Db\Entity;
 use OCP\AppFramework\Db\QBMapper;
 use OCP\DB\QueryBuilder\IQueryBuilder;
@@ -35,7 +36,7 @@ abstract class DeckMapper extends QBMapper {
 
 	/**
 	 * @param $id
-	 * @return \OCP\AppFramework\Db\Entity if not found
+	 * @return T
 	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
 	 * @throws \OCP\AppFramework\Db\DoesNotExistException
 	 */
@@ -47,4 +48,21 @@ abstract class DeckMapper extends QBMapper {
 
 		return $this->findEntity($qb);
 	}
+
+	/**
+	 * Helper function to split passed array into chunks of 1000 elements and
+	 * call a given callback for fetching query results
+	 *
+	 * Can be useful to limit to 1000 results per query for oracle compatiblity
+	 * but still iterate over all results
+	 */
+	public function chunkQuery(array $ids, callable $callback): Generator {
+		$limit = 1000;
+		while (!empty($ids)) {
+			$slice = array_splice($ids, 0, $limit);
+			foreach ($callback($slice) as $item) {
+				yield $item;
+			}
+		}
+	}
 }