[Bug]: Can't fetch All Contacts: PHP Fatal error: Allowed memory size of 536870912 bytes exhausted

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

When trying to display All contacts, an error is thrown server side. See PHP logs.
We've grown the PHP memory_limit to several GiB of RAM without success. It seems that the generated array is too big.

Steps to reproduce

1. Go to contacts app
2. Wait for server to fetch all contacts (+22K from LDAP)
3. Observe 500 error on browser console

Expected behavior

Contacts are fetched.

Installation method

None

Nextcloud Server version

27

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.2

Web server

Apache (supported)

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

Upgraded to a MAJOR version (ex. 22 to 23)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

PHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 28672 bytes) in /var/www/nextcloud/3rdparty/doctrine/dbal/src/Driver/PDO/Result.php on line 104" while reading response, request: "REPORT /remote.php/dav/addressbooks/users/user.test@cloud.com/z-server-generated--system/ HTTP/1.1"

PHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 24576 bytes) in /var/www/nextcloud/apps/dav/lib/CardDAV/CardDavBackend.php on line 1045" while reading response, request: "REPORT /remote.php/dav/addressbooks/users/user.test@cloud.com/z-server-generated--system/ HTTP/1.1"

Additional info

No response

Inspect apps/dav/lib/CardDAV/CardDavBackend.php at line 1045 and 3rdparty/doctrine/dbal/src/Driver/PDO/Result.php at line 104. Reproduce the REPORT request against an address book with more than 22,000 LDAP contacts and trace the memory failure; done means All Contacts can be fetched without a 500 response or PHP memory exhaustion.