More than 1000 expressions in a list are not allowed on Oracle

What happens: When the Deck app builds a calendar view, it asks the database for labels assigned to a large number of cards all at once. The database call fails with the error "More than 1000 expressions in a list are not allowed on Oracle." As a result the calendar/Caldav request fails and an error is written to the logs.

Important note about logging: we see and log this same error message even on non‑Oracle systems. The application constructs an IN(...) list with >1000 placeholders and the DB access layer (Doctrine/DBAL) raises a QueryException with that message. Because the exception message is generated/recorded by the DB/DBAL layer, it appears in logs regardless of whether the backend is actually Oracle.

I saw today the same error on a Nextcloud 28.0.7.4 on cadav requests:

Assistent
Bildgenerirung{
  "reqId": "h4GkaBMxZBbaYGvGCNf6",
  "level": 3,
  "time": "2024-07-12T17:16:45+00:00",
  "remoteAddr": "2a0f:6480:1::2",
  "user": "abb8c2f2-26c2-1034-821f-c3ab67df07dc",
  "app": "core",
  "method": "REPORT",
  "url": "/remote.php/caldav/calendars/abb8c2f2-26c2-1034-821f-c3ab67df07dc/app-generated--deck--board-27/",
  "message": "More than 1000 expressions in a list are not allowed on Oracle.",
  "userAgent": "Evolution/3.46.4",
  "version": "28.0.7.4",
  "exception": {
    "Exception": "Doctrine\\DBAL\\Query\\QueryException",
    "Message": "More than 1000 expressions in a list are not allowed on Oracle.",
    "Code": 0,
    "Trace": [
      {
        "file": "/var/www/nextcloud/lib/private/DB/QueryBuilder/QueryBuilder.php",
        "line": 293,
        "function": "execute",
        "class": "OC\\DB\\QueryBuilder\\QueryBuilder",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/lib/public/AppFramework/Db/QBMapper.php",
        "line": 335,
        "function": "executeQuery",
        "class": "OC\\DB\\QueryBuilder\\QueryBuilder",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/apps/deck/lib/Db/LabelMapper.php",
        "line": 92,
        "function": "findEntities",
        "class": "OCP\\AppFramework\\Db\\QBMapper",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/apps/deck/lib/Service/CardService.php",
        "line": 146,
        "function": "findAssignedLabelsForCards",
        "class": "OCA\\Deck\\Db\\LabelMapper",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/apps/deck/lib/Service/CardService.php",
        "line": 207,
        "function": "enrichCards",
        "class": "OCA\\Deck\\Service\\CardService",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/apps/deck/lib/DAV/DeckCalendarBackend.php",
        "line": 85,
        "function": "findCalendarEntries",
        "class": "OCA\\Deck\\Service\\CardService",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/apps/deck/lib/DAV/Calendar.php",
        "line": 152,
        "function": "getChildren",
        "class": "OCA\\Deck\\DAV\\DeckCalendarBackend",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/apps/deck/lib/DAV/Calendar.php",
        "line": 135,
        "function": "getBackendChildren",
        "class": "OCA\\Deck\\DAV\\Calendar",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/apps/deck/lib/DAV/Calendar.php",
        "line": 90,
        "function": "getChildren",
        "class": "OCA\\Deck\\DAV\\Calendar",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Plugin.php",
        "line": 598,
        "function": "calendarQuery",
        "class": "OCA\\Deck\\DAV\\Calendar",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Plugin.php",
        "line": 258,
        "function": "calendarQueryReport",
        "class": "Sabre\\CalDAV\\Plugin",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php",
        "line": 89,
        "function": "report",
        "class": "Sabre\\CalDAV\\Plugin",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php",
        "line": 690,
        "function": "emit",
        "class": "Sabre\\DAV\\Server",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php",
        "line": 89,
        "function": "httpReport",
        "class": "Sabre\\DAV\\CorePlugin",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php",
        "line": 472,
        "function": "emit",
        "class": "Sabre\\DAV\\Server",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php",
        "line": 253,
        "function": "invokeMethod",
        "class": "Sabre\\DAV\\Server",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php",
        "line": 321,
        "function": "start",
        "class": "Sabre\\DAV\\Server",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/apps/dav/appinfo/v1/caldav.php",
        "line": 123,
        "function": "exec",
        "class": "Sabre\\DAV\\Server",
        "type": "->"
      },
      {
        "file": "/var/www/nextcloud/remote.php",
        "line": 172,
        "args": [
          "/var/www/nextcloud/apps/dav/appinfo/v1/caldav.php"
        ],
        "function": "require_once"
      }
    ],
    "File": "/var/www/nextcloud/lib/private/DB/QueryBuilder/QueryBuilder.php",
    "Line": 263,
    "message": "More than 1000 expressions in a list are not allowed on Oracle.",
    "query": "SELECT `l`.*, `card_id` FROM `*PREFIX*deck_labels` `l` INNER JOIN `*PREFIX*deck_assigned_labels` `al` ON l.id = al.label_id WHERE `card_id` IN (:dcValue1) ORDER BY `l`.`id` ASC",
    "exception": {},
    "CustomMessage": "More than 1000 expressions in a list are not allowed on Oracle."
  }
}

Originally posted by @schiessle in https://github.com/nextcloud/server/issues/32593#issuecomment-2226008846

Start in apps/deck/lib/Db/LabelMapper.php at line 92, where findAssignedLabelsForCards reaches the query builder, then follow CardService.php and DeckCalendarBackend.php. Reproduce with a CalDAV calendar request containing more than 1000 cards and inspect the generated IN query. Done means large card lists no longer fail and the request completes without this logged exception.