global class SnapshotOpenCasesBatch implements Database.Batchable<sObject> 
 {

    //Gather all the records I want to use in the execute method
    global Database.QueryLocator start(Database.BatchableContext BC) 
    {
        return Database.getQueryLocator([SELECT ID, OwnerID, Name, Case_Type__c, Subtype__c, Status__c, Reason__c, Case_Age_Days__c, CreatedDate FROM Custom_Case__c WHERE Status__c in ('New', 'Work in Process', 'Escalated', 'Solution Proposed/Validation') ORDER BY CreatedDate ASC]); // Production source field is Created_Date__c
    }

    global void execute(Database.BatchableContext BC, List<Custom_Case__c> openCases) 
    {

            //for creating new Snapshot batch.
            List<Snapshot_Open_CASE__c> newSnapshot = new List<Snapshot_Open_CASE__c>();

            //create map collection to pair case owner ID and full name 
            Map<ID, String> userMap = new Map<ID, String>(); 

            //add all OwnerId values from openCases List to the set of userIds for query
            Set<ID> userIdSet = new Set<ID>();

            for (Custom_Case__c c : openCases) {
                userIdSet.add(c.OwnerID);
            }

            //Go get all the User ID + name combos from the set of Ids created above
            List<User> userList = new List<User>([SELECT ID, Name FROM User WHERE ID in : userIdSet]);

            //Load userMap with the results of the query above
            for(User u : userList){
                userMap.put(u.id, u.Name);
            }   

            for (Custom_Case__c c : openCases) {
                Snapshot_Open_CASE__c snap = new Snapshot_Open_CASE__c();
                snap.CASE_ID__c = c.ID;
                snap.OwnerID__c = c.OwnerID;
                snap.Case_Number__c = c.Name;
                snap.Case_Type__c = c.Case_Type__c;
                snap.Subtype__c = c.Subtype__c;
                snap.Status__c = c.Status__c;
                snap.Reason__c = c.Reason__c;
                snap.Case_Age_Days__c = c.Case_Age_Days__c;
                snap.Created_Date__c = c.CreatedDate.date(); // Production source field is Created_Date__c // also convert datetime to date
                snap.Name = String.valueof(Date.today()); // Use execution date as unique id

                // add the user name
                snap.Owner_Full_Name__c = userMap.get(c.OwnerId);

                //load up the data for insert
                newSnapshot.add(snap);
                }

            insert newSnapshot;
            }

    global void finish(Database.BatchableContext BC) {
        system.debug('Batch Job is Complete');
    }
}