how to fetch contact custom fields from task object

Question

I have below query fetching contact fields and task fields from task object

SELECT Id,Who.Name, Subject,Description, ActivityDate, Status, OwnerId, CreatedBy.Name, 
                         CreatedDate,LastModifiedById FROM Task

but when I change who.name to any who.CustomFieldFromContact__c object, I get an error

CustomFieldFromContact__c is a date field

can someone please suggest how to fetch custom contact fields from task object?

Answer 1

Unfortunately there isn't any way to do this.

The Who field is a polymorphic relationship that can point to either a Contact or User. Because of this, traversing the relationship via the dot notation isn't currently possible.

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Essentially you'll need to query your tasks, create a list of who ids, then separately query the Contact table and join them together in your own code.