perf: improve DB queries

lib/Db/AttachmentMapper.php

@@ -64,6 +64,34 @@ public function findByData(int $cardId, string $data): Attachment {
 		return $this->findEntity($qb);
 	}
 
+	/**
+	 * Returns a map of cardId => attachment count for the given card IDs in a single query.
+	 *
+	 * @param int[] $cardIds
+	 * @return array<int, int>
+	 * @throws \OCP\DB\Exception
+	 */
+	public function findCountByCardIds(array $cardIds): array {
+		if (empty($cardIds)) {
+			return [];
+		}
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('card_id')
+			->selectAlias($qb->func()->count('id'), 'attachment_count')
+			->from($this->getTableName())
+			->where($qb->expr()->in('card_id', $qb->createNamedParameter($cardIds, IQueryBuilder::PARAM_INT_ARRAY)))
+			->andWhere($qb->expr()->eq('deleted_at', $qb->createNamedParameter(0, IQueryBuilder::PARAM_INT)))
+			->groupBy('card_id');
+
+		$counts = [];
+		$cursor = $qb->executeQuery();
+		while ($row = $cursor->fetch()) {
+			$counts[(int)$row['card_id']] = (int)$row['attachment_count'];
+		}
+		$cursor->closeCursor();
+		return $counts;
+	}
+
 	/**
 	 * @return Entity[]
 	 * @throws \OCP\DB\Exception

lib/Db/BoardMapper.php

@@ -163,12 +163,14 @@ public function findAllForUser(string $userId, ?int $since = null, bool $include
 				return $board->getId();
 			}, $allBoards));
 
+			// Pre-group ACLs by board ID
+			$aclsByBoard = [];
+			foreach ($acls as $acl) {
+				$aclsByBoard[$acl->getBoardId()][] = $acl;
+			}
 			/* @var Board $entry */
 			foreach ($allBoards as $entry) {
-				$boardAcls = array_values(array_filter($acls, function ($acl) use ($entry) {
-					return $acl->getBoardId() === $entry->getId();
-				}));
-				$entry->setAcl($boardAcls);
+				$entry->setAcl($aclsByBoard[$entry->getId()] ?? []);
 			}
 
 			foreach ($allBoards as $board) {

lib/Db/CardMapper.php

@@ -237,7 +237,7 @@ public function findCalendarEntries(int $boardId, ?int $limit = null, $offset =
 		return $this->findEntities($qb);
 	}
 
-	public function findAllArchived($stackId, $limit = null, $offset = null) {
+	public function findAllArchived(int $stackId, ?int $limit = null, ?int $offset = null): array {
 		$qb = $this->db->getQueryBuilder();
 		$qb->select('*')
 			->from('deck_cards')
@@ -250,7 +250,33 @@ public function findAllArchived($stackId, $limit = null, $offset = null) {
 		return $this->findEntities($qb);
 	}
 
-	public function findAllByStack($stackId, $limit = null, $offset = null) {
+	/**
+	 * Batch-fetch all archived cards for multiple stacks in a single query.
+	 *
+	 * @param int[] $stackIds
+	 * @return array<int, Card[]> Map of stackId => Card[]
+	 * @throws \OCP\DB\Exception
+	 */
+	public function findAllArchivedForStacks(array $stackIds): array {
+		if (empty($stackIds)) {
+			return [];
+		}
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('*')
+			->from('deck_cards')
+			->where($qb->expr()->in('stack_id', $qb->createNamedParameter($stackIds, IQueryBuilder::PARAM_INT_ARRAY)))
+			->andWhere($qb->expr()->eq('archived', $qb->createNamedParameter(true, IQueryBuilder::PARAM_BOOL)))
+			->andWhere($qb->expr()->eq('deleted_at', $qb->createNamedParameter(0, IQueryBuilder::PARAM_INT)))
+			->orderBy('last_modified');
+
+		$cards = array_fill_keys($stackIds, []);
+		foreach ($this->findEntities($qb) as $card) {
+			$cards[$card->getStackId()][] = $card;
+		}
+		return $cards;
+	}
+
+	public function findAllByStack(int $stackId, ?int $limit = null, ?int $offset = null): array {
 		$qb = $this->db->getQueryBuilder();
 		$qb->select('*')
 			->from('deck_cards')

lib/Db/LabelMapper.php

@@ -33,6 +33,30 @@ public function findAll(int $boardId, ?int $limit = null, int $offset = 0): arra
 		return $this->findEntities($qb);
 	}
 
+	/**
+	 * Check if a label with the given title already exists on the board.
+	 * Pass $excludeId to skip a specific label (used during updates).
+	 *
+	 * @throws \OCP\DB\Exception
+	 */
+	public function existsByBoardIdAndTitle(int $boardId, string $title, ?int $excludeId = null): bool {
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('id')
+			->from($this->getTableName())
+			->where($qb->expr()->eq('board_id', $qb->createNamedParameter($boardId, IQueryBuilder::PARAM_INT)))
+			->andWhere($qb->expr()->eq('title', $qb->createNamedParameter($title, IQueryBuilder::PARAM_STR)))
+			->setMaxResults(1);
+
+		if ($excludeId !== null) {
+			$qb->andWhere($qb->expr()->neq('id', $qb->createNamedParameter($excludeId, IQueryBuilder::PARAM_INT)));
+		}
+
+		$cursor = $qb->executeQuery();
+		$exists = $cursor->fetch() !== false;
+		$cursor->closeCursor();
+		return $exists;
+	}
+
 	public function delete(Entity $entity): Entity {
 		// delete assigned labels
 		$this->deleteLabelAssignments($entity->getId());

lib/Db/StackMapper.php

@@ -53,6 +53,43 @@ public function find(int $id): Stack {
 		return $this->stackCache[(string)$id];
 	}
 
+	/**
+	 * Fetch multiple stacks by their IDs in a single query.
+	 *
+	 * @param int[] $ids
+	 * @return array<int, Stack> Map of stackId => Stack
+	 * @throws \OCP\DB\Exception
+	 */
+	public function findByIds(array $ids): array {
+		if (empty($ids)) {
+			return [];
+		}
+
+		$stacks = [];
+		$uncachedIds = [];
+		foreach ($ids as $id) {
+			if (isset($this->stackCache[(string)$id])) {
+				$stacks[$id] = $this->stackCache[(string)$id];
+			} else {
+				$uncachedIds[] = $id;
+			}
+		}
+
+		if (!empty($uncachedIds)) {
+			$qb = $this->db->getQueryBuilder();
+			$qb->select('*')
+				->from($this->getTableName())
+				->where($qb->expr()->in('id', $qb->createNamedParameter($uncachedIds, IQueryBuilder::PARAM_INT_ARRAY)));
+
+			foreach ($this->findEntities($qb) as $stack) {
+				$this->stackCache[(string)$stack->getId()] = $stack;
+				$stacks[$stack->getId()] = $stack;
+			}
+		}
+
+		return $stacks;
+	}
+
 	/**
 	 * @throws \OCP\DB\Exception
 	 */

lib/Service/AttachmentService.php

@@ -137,21 +137,57 @@ public function findAll(int $cardId, bool $withDeleted = false): array {
 	 * @throws \OCP\DB\Exception
 	 */
 	public function count(int $cardId): int {
-		$count = $this->attachmentCacheHelper->getAttachmentCount($cardId);
-		if ($count === null) {
-			$count = count($this->attachmentMapper->findAll($cardId));
-
-			foreach (array_keys($this->services) as $attachmentType) {
-				$service = $this->getService($attachmentType);
-				if ($service instanceof ICustomAttachmentService) {
-					$count += $service->getAttachmentCount($cardId);
+		return ($this->countForCards([$cardId]))[$cardId] ?? 0;
+	}
+
+	/**
+	 * Returns a map of cardId => attachment count for the given card IDs using batch queries.
+	 *
+	 * @param int[] $cardIds
+	 * @return array<int, int>
+	 * @throws \OCP\DB\Exception
+	 */
+	public function countForCards(array $cardIds): array {
+		if (empty($cardIds)) {
+			return [];
+		}
+
+		$counts = [];
+		$uncachedIds = [];
+		foreach ($cardIds as $cardId) {
+			$cached = $this->attachmentCacheHelper->getAttachmentCount($cardId);
+			if ($cached !== null) {
+				$counts[$cardId] = $cached;
+			} else {
+				$uncachedIds[] = $cardId;
+				$counts[$cardId] = 0;
+			}
+		}
+
+		if (empty($uncachedIds)) {
+			return $counts;
+		}
+
+		// Batch query for deck_file attachments stored in the deck_attachment table
+		foreach ($this->attachmentMapper->findCountByCardIds($uncachedIds) as $cardId => $count) {
+			$counts[$cardId] = $count;
+		}
+
+		// Add counts from custom attachment services (e.g. files shared via FilesAppService)
+		foreach (array_keys($this->services) as $attachmentType) {
+			$service = $this->getService($attachmentType);
+			if ($service instanceof ICustomAttachmentService) {
+				foreach ($service->getAttachmentCountForCards($uncachedIds) as $cardId => $count) {
+					$counts[$cardId] = ($counts[$cardId] ?? 0) + $count;
 				}
 			}
+		}
 
-			$this->attachmentCacheHelper->setAttachmentCount($cardId, $count);
+		foreach ($uncachedIds as $cardId) {
+			$this->attachmentCacheHelper->setAttachmentCount($cardId, $counts[$cardId]);
 		}
 
-		return $count;
+		return $counts;
 	}
 
 	/**

lib/Service/BoardService.php

@@ -721,13 +721,14 @@ private function cloneCards(Board $board, Board $newBoard, bool $withAssignments
 		usort($stacks, $stackSorter);
 		usort($newStacks, $stackSorter);
 
+		$stackIds = array_map(fn (Stack $stack) => $stack->getId(), $stacks);
+		$activeCardsByStack = $this->cardMapper->findAllForStacks($stackIds);
+		$archivedCardsByStack = $this->cardMapper->findAllArchivedForStacks($stackIds);
+
 		$i = 0;
 		foreach ($stacks as $stack) {
-			$cards = $this->cardMapper->findAll($stack->getId());
-			$archivedCards = $this->cardMapper->findAllArchived($stack->getId());
-
 			/** @var Card[] $cards */
-			$cards = array_merge($cards, $archivedCards);
+			$cards = array_merge($activeCardsByStack[$stack->getId()] ?? [], $archivedCardsByStack[$stack->getId()] ?? []);
 
 			foreach ($cards as $card) {
 				$targetStackId = $moveCardsToLeftStack ? $newStacks[0]->getId() : $newStacks[$i]->getId();
@@ -830,22 +831,38 @@ private function clearBoardFromCache(Board $board): void {
 
 	private function enrichWithCards(Board $board): void {
 		$stacks = $this->stackMapper->findAll($board->getId());
+		if (\count($stacks) === 0) {
+			return;
+		}
+
+		$stackIds = array_map(fn (Stack $stack) => $stack->getId(), $stacks);
+
+		// Fetch all active cards for all stacks in one query
+		$cardsByStack = $this->cardMapper->findAllForStacks($stackIds);
+
+		$allCards = array_merge(...array_values(array_filter($cardsByStack)));
+		$allCardIds = array_map(fn (Card $card) => $card->getId(), $allCards);
+
+		// Batch-fetch labels and assigned users for all cards
+		$labelsByCard = [];
+		foreach ($this->labelMapper->findAssignedLabelsForCards($allCardIds) as $label) {
+			$labelsByCard[$label->getCardId()][] = $label;
+		}
+		$usersByCard = [];
+		foreach ($this->assignedUsersMapper->findIn($allCardIds) as $assignment) {
+			$usersByCard[$assignment->getCardId()][] = $assignment;
+		}
+
 		foreach ($stacks as $stack) {
-			$cards = $this->cardMapper->findAllByStack($stack->getId());
 			$fullCards = [];
-			foreach ($cards as $card) {
-				$fullCard = $this->cardMapper->find($card->getId());
-				$assignedUsers = $this->assignedUsersMapper->findAll($card->getId());
-				$fullCard->setAssignedUsers($assignedUsers);
-				array_push($fullCards, $fullCard);
+			foreach ($cardsByStack[$stack->getId()] ?? [] as $card) {
+				$card->setLabels($labelsByCard[$card->getId()] ?? []);
+				$card->setAssignedUsers($usersByCard[$card->getId()] ?? []);
+				$fullCards[] = $card;
 			}
 			$stack->setCards($fullCards);
 		}
 
-		if (\count($stacks) === 0) {
-			return;
-		}
-
 		$board->setStacks($stacks);
 	}
 }

lib/Service/CardService.php

@@ -11,13 +11,11 @@
 use OCA\Deck\Activity\ChangeSet;
 use OCA\Deck\BadRequestException;
 use OCA\Deck\Db\Acl;
-use OCA\Deck\Db\Assignment;
 use OCA\Deck\Db\AssignmentMapper;
 use OCA\Deck\Db\BoardMapper;
 use OCA\Deck\Db\Card;
 use OCA\Deck\Db\CardMapper;
 use OCA\Deck\Db\ChangeHelper;
-use OCA\Deck\Db\Label;
 use OCA\Deck\Db\LabelMapper;
 use OCA\Deck\Db\StackMapper;
 use OCA\Deck\Event\CardCreatedEvent;
@@ -71,12 +69,19 @@ public function __construct(
 	public function enrichCards(array $cards): array {
 		$user = $this->userManager->get($this->userId);
 
-		$cardIds = array_map(function (Card $card) use ($user): int {
+		$allCardIds = array_map(fn (Card $card) => $card->getId(), $cards);
+		$attachmentCounts = $this->attachmentService->countForCards($allCardIds);
+
+		// Pre-fetch all stacks for this batch in one query and index by ID
+		$stackIds = array_unique(array_map(fn (Card $card) => $card->getStackId(), $cards));
+		$stacksById = $this->stackMapper->findByIds($stackIds);
+
+		$cardIds = array_map(function (Card $card) use ($user, $attachmentCounts, $stacksById): int {
 			// Everything done in here might be heavy as it is executed for every card
 			$cardId = $card->getId();
 			$this->cardMapper->mapOwner($card);
 
-			$card->setAttachmentCount($this->attachmentService->count($cardId));
+			$card->setAttachmentCount($attachmentCounts[$cardId] ?? 0);
 
 			// TODO We should find a better way just to get the comment count so we can save 1-3 queries per card here
 			$countComments = $this->commentsManager->getNumberOfCommentsForObject('deckCard', (string)$card->getId());
@@ -85,7 +90,7 @@ public function enrichCards(array $cards): array {
 			$card->setCommentsUnread($countUnreadComments);
 			$card->setCommentsCount($countComments);
 
-			$stack = $this->stackMapper->find($card->getStackId());
+			$stack = $stacksById[$card->getStackId()] ?? $this->stackMapper->find($card->getStackId());
 			$board = $this->boardService->find($stack->getBoardId(), false);
 			$card->setRelatedStack($stack);
 			$card->setRelatedBoard($board);
@@ -96,15 +101,19 @@ public function enrichCards(array $cards): array {
 		$assignedLabels = $this->labelMapper->findAssignedLabelsForCards($cardIds);
 		$assignedUsers = $this->assignedUsersMapper->findIn($cardIds);
 
+		// Pre-group labels and users by card ID
+		$labelsByCard = [];
+		foreach ($assignedLabels as $label) {
+			$labelsByCard[$label->getCardId()][] = $label;
+		}
+		$usersByCard = [];
+		foreach ($assignedUsers as $assignment) {
+			$usersByCard[$assignment->getCardId()][] = $assignment;
+		}
+
 		foreach ($cards as $card) {
-			$cardLabels = array_values(array_filter($assignedLabels, function (Label $label) use ($card) {
-				return $label->getCardId() === $card->getId();
-			}));
-			$cardAssignedUsers = array_values(array_filter($assignedUsers, function (Assignment $assignment) use ($card) {
-				return $assignment->getCardId() === $card->getId();
-			}));
-			$card->setLabels($cardLabels);
-			$card->setAssignedUsers($cardAssignedUsers);
+			$card->setLabels($labelsByCard[$card->getId()] ?? []);
+			$card->setAssignedUsers($usersByCard[$card->getId()] ?? []);
 		}
 
 		return array_map(