Map<Id, Contact> cons = new Map<Id, Contact> ([
    SELECT Id, Organization__c
    FROM Contact
    WHERE Organization__c = 'FXCMASIA'
]);


List<Task> result = [
    SELECT Id, AccountId, ActivityDate, Comments__c, CreatedDate, Created_Date_Time__c, Department__c, Description, Details__c,
    OwnerId, Phone_Number__c, Priority, Status, Subject, Subject_Comments__c, WhatId, WhoId
    FROM Task
    WHERE (WhoId IN: cons.keySet())
    ORDER BY Id ASC
];

Set<Id> ids = new Set<Id>();
for (Task t:result) {
    ids.add(t.Id);
}

List<String> fields = new List<String> { 'Id', 'AccountId', 'ActivityDate', 'Comments__c', 'CreatedDate', 'Created_Date_Time__c', 'Department__c', 'Description', 'Details__c', 'OwnerId', 'Phone_Number__c', 'Priority', 'Status', 'Subject', 'Subject_Comments__c', 'WhatId', 'WhoId' };
System.debug(ids.size());

XMLCreator batch = new XMLCreator(ids, 'Task', fields, 'dboychev@fxcm.com', 'TasksRelatedToCase');
Database.executeBatch(batch, 200);