Add support for WebDAV SEARCH on nc:metadata-photos-original_date_time, fileId and internal id field

Support deterministic cursor pagination in WebDAV SEARCH using oc:fileid

Motivation

Nextcloud clients need to retrieve large media collections through bounded WebDAV SEARCH requests.

Media results are primarily ordered by a date property such as:

• DAV:getlastmodified
• nc:upload_time
• nc:metadata-photos-original_date_time

A date is not unique. Hundreds or thousands of files can share the same timestamp. Date-only cursor pagination can therefore stop advancing when all results in a limited response have the same date.

Missing capability

The client needs a deterministic secondary key:

date DESC, oc:fileid DESC

The next request can then continue using the last tuple returned by the previous page:

date < cursorDate
OR
(date = cursorDate AND oc:fileid < cursorFileId)

The current search backend declares oc:fileid selectable and searchable, but not sortable. See [FileSearchBackend.php](https://github.com/nextcloud/server/blob/master/apps/dav/lib/Files/FileSearchBackend.php).

DAV:displayname cannot be used as a replacement. Although it is sortable, a range comparison currently fails with:

HTTP 500
Unsupported comparison for field name: lte

Using only a result limit therefore cannot guarantee progress when many files share the same date.

Example request

This example retrieves the next media page after:

cursorDate   = 2026-06-01T10:00:00Z
cursorFileId = 123456

<?xml version="1.0" encoding="UTF-8"?>
<d:searchrequest
    xmlns:d="DAV:"
    xmlns:oc="http://owncloud.org/ns"
    xmlns:nc="http://nextcloud.org/ns">
    <d:basicsearch>
        <d:select>
            <d:prop>
                <oc:id/>
                <oc:fileid/>
                <d:displayname/>
                <d:getlastmodified/>
                <d:getcontenttype/>
                <d:getetag/>
            </d:prop>
        </d:select>

        <d:from>
            <d:scope>
                <d:href>/files/test</d:href>
                <d:depth>infinity</d:depth>
            </d:scope>
        </d:from>

        <d:where>
            <d:and>
                <d:or>
                    <d:like>
                        <d:prop><d:getcontenttype/></d:prop>
                        <d:literal>image/%</d:literal>
                    </d:like>
                    <d:like>
                        <d:prop><d:getcontenttype/></d:prop>
                        <d:literal>video/%</d:literal>
                    </d:like>
                </d:or>

                <d:or>
                    <d:lt>
                        <d:prop><d:getlastmodified/></d:prop>
                        <d:literal>2026-06-01T10:00:00Z</d:literal>
                    </d:lt>

                    <d:and>
                        <d:eq>
                            <d:prop><d:getlastmodified/></d:prop>
                            <d:literal>2026-06-01T10:00:00Z</d:literal>
                        </d:eq>

                        <d:lt>
                            <d:prop><oc:fileid/></d:prop>
                            <d:literal>123456</d:literal>
                        </d:lt>
                    </d:and>
                </d:or>
            </d:and>
        </d:where>

        <d:orderby>
            <d:order>
                <d:prop><d:getlastmodified/></d:prop>
                <d:descending/>
            </d:order>
            <d:order>
                <d:prop><oc:fileid/></d:prop>
                <d:descending/>
            </d:order>
        </d:orderby>

        <d:limit>
            <d:nresults>1000</d:nresults>
        </d:limit>
    </d:basicsearch>
</d:searchrequest>

The same cursor pattern should be usable with nc:metadata-photos-original_date_time as the primary date property when that indexed metadata field is available.

Requested behavior

• Allow oc:fileid in d:orderby.
• Continue supporting numeric comparisons on oc:fileid, including lt, lte, gt, gte and eq.
• Allow indexed nc:metadata-photos-original_date_time metadata to be selected, filtered and ordered.
• Preserve oc:id in d:select so clients can deduplicate returned resources.

This does not require new metadata or a new indexing mechanism. It exposes existing indexed fields sufficiently for deterministic, bounded cursor pagination.

Expected result

Clients can process arbitrarily large media collections in bounded requests, including collections containing more than the request limit with the same timestamp, without using an effectively unlimited SEARCH request or risking a non-advancing cursor.

Start with apps/dav/lib/Files/FileSearchBackend.php and trace the WebDAV SEARCH handling it feeds. Check how oc:fileid and nc:metadata-photos-original_date_time are exposed for selection, comparisons, and ordering, while preserving oc:id. Done means the supplied cursor query supports numeric oc:fileid comparisons, secondary ordering, and the indexed metadata field without requiring new indexing.