Merge pull request #45968 from nextcloud/fix/dav/limit-sync-token-created-at-updates

fix(dav): Limit number of UPDATES for sync token created_at

apps/dav/lib/Migration/Version1025Date20240308063933.php

@@ -10,6 +10,7 @@ declare(strict_types=1);
 namespace OCA\DAV\Migration;
 
 use Closure;
+use OCP\AppFramework\Services\IAppConfig;
 use OCP\DB\ISchemaWrapper;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\DB\Types;
@@ -19,10 +20,13 @@ use OCP\Migration\SimpleMigrationStep;
 
 class Version1025Date20240308063933 extends SimpleMigrationStep {
 
+	private IAppConfig $appConfig;
 	private IDBConnection $db;
 
-	public function __construct(IDBConnection $db) {
+	public function __construct(IAppConfig $appConfig,
+		IDBConnection $db) {
 		$this->db = $db;
+		$this->appConfig = $appConfig;
 	}
 
 	/**
@@ -50,7 +54,22 @@ class Version1025Date20240308063933 extends SimpleMigrationStep {
 	}
 
 	public function postSchemaChange(IOutput $output, \Closure $schemaClosure, array $options): void {
+		// The threshold is higher than the default of \OCA\DAV\BackgroundJob\PruneOutdatedSyncTokensJob
+		// but small enough to fit into a cluster transaction size.
+		// For a 50k users instance that would still keep 10 changes on average.
+		$limit = max(1, (int) $this->appConfig->getAppValue('totalNumberOfSyncTokensToKeep', '500000'));
+
 		foreach (['addressbookchanges', 'calendarchanges'] as $tableName) {
+			$thresholdSelect = $this->db->getQueryBuilder();
+			$thresholdSelect->select('id')
+				->from($tableName)
+				->orderBy('id', 'desc')
+				->setFirstResult($limit)
+				->setMaxResults(1);
+			$oldestIdResult = $thresholdSelect->executeQuery();
+			$oldestId = $oldestIdResult->fetchColumn();
+			$oldestIdResult->closeCursor();
+
 			$qb = $this->db->getQueryBuilder();
 
 			$update = $qb->update($tableName)
@@ -59,7 +78,15 @@ class Version1025Date20240308063933 extends SimpleMigrationStep {
 					$qb->expr()->eq('created_at', $qb->createNamedParameter(0, IQueryBuilder::PARAM_INT)),
 				);
 
+			// If there is a lot of data we only set timestamp for the most recent rows
+			// because the rest will be deleted by \OCA\DAV\BackgroundJob\PruneOutdatedSyncTokensJob
+			// anyway.
+			if ($oldestId !== false) {
+				$update->andWhere($qb->expr()->gt('id', $qb->createNamedParameter($oldestId, IQueryBuilder::PARAM_INT), IQueryBuilder::PARAM_INT));
+			}
+
 			$updated = $update->executeStatement();
+
 			$output->debug('Added a default creation timestamp to ' . $updated . ' rows in ' . $tableName);
 		}
 	}