In this case we will upload 25000 contacts approximately from iPhone with groups, and this app will removed duplicate contacts at iPhone, the Other contacts will upload to Google.
At next time, we will edit a contact, create a new contact, and remove a contact at iPhone, after that lunch this app, this app should be suggestion update 1, create 1 to Google, and remove 1 at iPhone.
Prepare the test environment
This image is removing all contacts at iPhone.
1. Sign in Google account with email@example.com, and remove all groups and all contacts by "Super Tools".
2. Set Local container as default container while the test device have more account, then Remove all contacts and all groups at iPhone by "Super Tools".
3. create "Duplicate 10K Contacts" twice, and create "Create 10K contacts" by test tool.
4. create a group abc by "Group Manger", add add 2 contacts into this group.
Therefore, We have prepared 30, 000 contacts include duplicate, and 1 group with 2 member in it, The account of Google is empty.
Device: iPhone 6 iOS 12.1 16G
Run Sync Contacts
This image shows that 1860 contacts is duplicated, and the other 28140 contacts will be upload to Google.
press "Allow Now!"
Failed for more than 27000 contacts, because the Google account maximum is 27000. sometime, the uploaded contacts less than 27000 but more than 26950, because this app batch upload 50 contact once.
27000 contact has appeared in this account, and the group "abc" has created with 2 contacts in it.
Run Sync again after edit a contact, remove a contact and create a new contact
This image shows that "Remove 1 contact" because we have remove a contact at iPhone, "Upload 1141 contacts" because the new contact and failed contact need upload again, "Update 1 contact" because we have edit a contact.
drop bottom in this view
"Normal 26998 contact" because those contacts is same with contacts in Google account.
press "Allow Now!" to action sync again.Contact of Google account have 26999 after sync again.(Full Image)
removed a contact because this contact have removed at iPhone.
More than 27000 contacts can NOT upload because the limitation of Google account.
Therefore, please sync don't more than 27000 contacts exclude duplicate from your iPhone, and removed, edited, created contact will action in Google account after sync again.
In the End, 28140 contacts at iPhone, because 1860 duplicate contacts has removed from 30000 in first sync, remove 1 and create new 1 in second sync.
Thanks for you time, and question please send email to firstname.lastname@example.org.