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global class UpdateContactAddresses implements 
 Database.Batchable<sobject>, Database.Stateful {
 
 // instance member to retain state across transactions
 global Integer recordsProcessed = 0;

 global Database.QueryLocator start(Database.BatchableContext bc) {
 return Database.getQueryLocator(
 'SELECT ID, BillingStreet, BillingCity, BillingState, ' +
 'BillingPostalCode, (SELECT ID, MailingStreet, MailingCity, ' +
 'MailingState, MailingPostalCode FROM Contacts) FROM Account ' + 
 'Where BillingCountry = \'USA\''
 );
 }

 global void execute(Database.BatchableContext bc, List<account> scope){
 // process each batch of records
 List<contact> contacts = new List<contact>();
 for (Account account : scope) {
 for (Contact contact : account.contacts) {
 contact.MailingStreet = account.BillingStreet;
 contact.MailingCity = account.BillingCity;
 contact.MailingState = account.BillingState;
 contact.MailingPostalCode = account.BillingPostalCode;
 // add contact to list to be updated
 contacts.add(contact);
 // increment the instance member counter
 recordsProcessed = recordsProcessed + 1;
 }
 }
 update contacts;
 } 

 global void finish(Database.BatchableContext bc){
 System.debug(recordsProcessed + ' records processed. Shazam!');
 AsyncApexJob job = [SELECT Id, Status, NumberOfErrors, 
 JobItemsProcessed,
 TotalJobItems, CreatedBy.Email
 FROM AsyncApexJob
 WHERE Id = :bc.getJobId()];
 // call some utility to send email
 EmailUtils.sendMessage(a, recordsProcessed);
 } 
}