fix: get all available previews on Oracle

Split the DB requests in chunk of 1000 for oracle compatibility.

Signed-off-by: Carl Schwan <[email protected]>

Author: CarlSchwan

lib/private/Preview/PreviewService.php

@@ -13,6 +13,7 @@
 use OC\Preview\Db\Preview;
 use OC\Preview\Db\PreviewMapper;
 use OC\Preview\Storage\StorageFactory;
+use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\IDBConnection;
 
 class PreviewService {
@@ -34,36 +35,52 @@ public function deletePreview(Preview $preview): void {
 	 * @return \Generator<array{storageId: int, fileIds: int[]}>
 	 */
 	public function getAvailableFileIds(): \Generator {
-		$maxQb = $this->connection->getQueryBuilder();
-		$maxQb->select($maxQb->func()->max('id'))
-			->from($this->previewMapper->getTableName())
-			->groupBy('file_id');
-
-		$qb = $this->connection->getQueryBuilder();
-		$qb->select('file_id', 'storage_id')
-			->from($this->previewMapper->getTableName())
-			->where($qb->expr()->in('id', $qb->createFunction($maxQb->getSQL())));
-
-		$result = $qb->executeQuery();
-
-		$lastStorageId = -1;
-		/** @var int[] $fileIds */
-		$fileIds = [];
-
-		// Previews next to each others in the database are likely in the same storage, so group them
-		while ($row = $result->fetch()) {
-			if ($lastStorageId !== (int)$row['storage_id']) {
-				if ($lastStorageId !== -1) {
-					yield ['storageId' => $lastStorageId, 'fileIds' => $fileIds];
-					$fileIds = [];
+		$lastId = null;
+		while (true) {
+			$maxQb = $this->connection->getQueryBuilder();
+			$maxQb->select($maxQb->func()->max('id'))
+				->from($this->previewMapper->getTableName())
+				->groupBy('file_id')
+				->setMaxResults(IQueryBuilder::MAX_IN_PARAMS);
+
+			$qb = $this->connection->getQueryBuilder();
+
+			if ($lastId !== null) {
+				$maxQb->andWhere($maxQb->expr()->gt('id', $qb->createNamedParameter($lastId)));
+			}
+
+			$qb->select('id', 'file_id', 'storage_id')
+				->from($this->previewMapper->getTableName())
+				->where($qb->expr()->in('id', $qb->createFunction($maxQb->getSQL())));
+
+			$result = $qb->executeQuery();
+
+			$lastStorageId = -1;
+			/** @var int[] $fileIds */
+			$fileIds = [];
+
+			$found = false;
+			// Previews next to each others in the database are likely in the same storage, so group them
+			while ($row = $result->fetch()) {
+				$found = true;
+				if ($lastStorageId !== (int)$row['storage_id']) {
+					if ($lastStorageId !== -1) {
+						yield ['storageId' => $lastStorageId, 'fileIds' => $fileIds];
+						$fileIds = [];
+					}
+					$lastStorageId = (int)$row['storage_id'];
 				}
-				$lastStorageId = (int)$row['storage_id'];
+				$fileIds[] = (int)$row['file_id'];
+				$lastId = $row['id'];
+			}
+
+			if (count($fileIds) > 0) {
+				yield ['storageId' => $lastStorageId, 'fileIds' => $fileIds];
 			}
-			$fileIds[] = (int)$row['file_id'];
-		}
 
-		if (count($fileIds) > 0) {
-			yield ['storageId' => $lastStorageId, 'fileIds' => $fileIds];
+			if (!$found) {
+				break;
+			}
 		}
 	}
 

lib/public/DB/QueryBuilder/IQueryBuilder.php

@@ -117,6 +117,12 @@ interface IQueryBuilder {
 	 */
 	public const MAX_ROW_DELETION = 100000;
 
+	/**
+	 * @since 33.0.0 Indicates how many params can be added in an IN condition
+	 * with an Oracle database server.
+	 */
+	public const MAX_IN_PARAMS = 1000;
+
 	/**
 	 * Enable/disable automatic prefixing of table names with the oc_ prefix
 	 *