Combining forces
As it's a prebuilt interface, leveraging the Database.Batchable interface is simple enough. There's very little required for you to take advantage of the Apex magic. On the surface, it seems like we could simply call our existing method from within the Execute() method and be done. However, it's important to remember our rules and ensure that we code as efficiently as possible. This means we need to ensure that we only operate on the records that need to be operated upon. To do this, we need to modify our code to query just the contacts that need to be updated.
Salesforce Object Query Language has the ability to include a Where clause in our query string. However, unlike SQL, it does not allow this Where clause to compare values of two different fields against each other. To do this most efficiently, we need to take off our programmer hats and put on our database administrator hats. Instead of writing code to determine whether a contact needs to be updated, we can create...
