fix(TaskProcessingApiController): Implement getNextScheduledTasks for next_batch endpoint

in order to avoid hitting the DB with multiple 1 row requests

Signed-off-by: Marcel Klehr <mklehr@gmx.net>

core/Controller/TaskProcessingApiController.php

@@ -576,6 +576,7 @@ class TaskProcessingApiController extends OCSController {
 
 	/**
 	 * Returns the next n scheduled tasks for the specified set of taskTypes and providers
+	 * The returned tasks are capped at ~50MiB
 	 *
 	 * @param list<string> $providerIds The ids of the providers
 	 * @param list<string> $taskTypeIds The ids of the task types
@@ -597,23 +598,18 @@ class TaskProcessingApiController extends OCSController {
 				]);
 			}
 
-			/** @var list<array{task:CoreTaskProcessingTask, provider:string}> $tasks */
-			$tasks = [];
-			$taskIdsToIgnore = [];
+			$tasks = $this->taskProcessingManager->getNextScheduledTasks($possibleTaskTypeIds, numberOfTasks: $numberOfTasks + 1);
+			$tasksJson = [];
 			// Stop when $numberOfTasks is reached or the json payload is larger than 50MiB
-			while (count($tasks) < $numberOfTasks && strlen(json_encode($tasks)) < 50 * 1024 * 1024) {
+			while (count($tasks) > 0 && count($tasksJson) < $numberOfTasks && strlen(json_encode($tasks)) < 50 * 1024 * 1024) {
 				// Until we find a task whose task type is set to be provided by the providers requested with this request
 				// Or no scheduled task is found anymore (given the taskIds to ignore)
-				try {
-					$task = $this->taskProcessingManager->getNextScheduledTask($possibleTaskTypeIds, $taskIdsToIgnore);
-				} catch (NotFoundException) {
-					break;
-				}
+				$task = array_shift($tasks);
 				try {
 					$provider = $this->taskProcessingManager->getPreferredProvider($task->getTaskTypeId());
 					if (in_array($provider->getId(), $possibleProviderIds, true)) {
 						if ($this->taskProcessingManager->lockTask($task)) {
-							$tasks[] = ['task' => $task->jsonSerialize(), 'provider' => $provider->getId()];
+							$tasksJson[] = ['task' => $task->jsonSerialize(), 'provider' => $provider->getId()];
 							continue;
 						}
 					}
@@ -621,16 +617,8 @@ class TaskProcessingApiController extends OCSController {
 					// There is no provider set for the task type of this task
 					// proceed to ignore this task
 				}
-
-				$taskIdsToIgnore[] = (int)$task->getId();
-			}
-
-			try {
-				$this->taskProcessingManager->getNextScheduledTask($possibleTaskTypeIds, $taskIdsToIgnore);
-				$hasMore = true;
-			} catch (\Throwable) {
-				$hasMore = false;
 			}
+			$hasMore = count($tasks) > 0;
 
 			return new DataResponse([
 				'tasks' => $tasks,

lib/private/TaskProcessing/Db/TaskMapper.php

@@ -233,4 +233,35 @@ class TaskMapper extends QBMapper {
 			return 0;
 		}
 	}
+
+	/**
+	 * @param list<string> $taskTypes
+	 * @param list<int> $taskIdsToIgnore
+	 * @param int $numberOfTasks
+	 * @return list<Task>
+	 * @throws Exception
+	 */
+	public function findNOldestScheduledByType(array $taskTypes, array $taskIdsToIgnore, int $numberOfTasks) {
+		$qb = $this->db->getQueryBuilder();
+		$qb->select(Task::$columns)
+			->from($this->tableName)
+			->where($qb->expr()->eq('status', $qb->createPositionalParameter(\OCP\TaskProcessing\Task::STATUS_SCHEDULED, IQueryBuilder::PARAM_INT)))
+			->setMaxResults($numberOfTasks)
+			->orderBy('last_updated', 'ASC');
+
+		if (!empty($taskTypes)) {
+			$filter = [];
+			foreach ($taskTypes as $taskType) {
+				$filter[] = $qb->expr()->eq('type', $qb->createPositionalParameter($taskType));
+			}
+
+			$qb->andWhere($qb->expr()->orX(...$filter));
+		}
+
+		if (!empty($taskIdsToIgnore)) {
+			$qb->andWhere($qb->expr()->notIn('id', $qb->createNamedParameter($taskIdsToIgnore, IQueryBuilder::PARAM_INT_ARRAY)));
+		}
+
+		return $this->findEntities($qb);
+	}
 }

lib/private/TaskProcessing/Manager.php

@@ -1192,6 +1192,18 @@ class Manager implements IManager {
 		}
 	}
 
+	public function getNextScheduledTasks(array $taskTypeIds = [], array $taskIdsToIgnore = [], int $numberOfTasks = 1): array {
+		try {
+			return array_map(fn ($taskEntity) => $taskEntity->toPublicTask(), $this->taskMapper->findNOldestScheduledByType($taskTypeIds, $taskIdsToIgnore, $numberOfTasks);
+		} catch (DoesNotExistException $e) {
+			throw new \OCP\TaskProcessing\Exception\NotFoundException('Could not find the task', 0, $e);
+		} catch (\OCP\DB\Exception $e) {
+			throw new \OCP\TaskProcessing\Exception\Exception('There was a problem finding the task', 0, $e);
+		} catch (\JsonException $e) {
+			throw new \OCP\TaskProcessing\Exception\Exception('There was a problem parsing JSON after finding the task', 0, $e);
+		}
+	}
+
 	/**
 	 * Takes task input data and replaces fileIds with File objects
 	 *

lib/public/TaskProcessing/IManager.php

@@ -160,6 +160,16 @@ interface IManager {
 	 */
 	public function getNextScheduledTask(array $taskTypeIds = [], array $taskIdsToIgnore = []): Task;
 
+	/**
+	 * @param list<string> $taskTypeIds
+	 * @param list<int> $taskIdsToIgnore
+	 * @param int $numberOfTasks
+	 * @return list<Task>
+	 * @throws Exception If the query failed
+	 * @since 33.0.0
+	 */
+	public function getNextScheduledTasks(array $taskTypeIds = [], array $taskIdsToIgnore = [], int $numberOfTasks = 1): array;
+
 	/**
 	 * @param int $id The id of the task
 	 * @param string|null $userId The user id that scheduled the task