[SalesForce] Attachment Cloning: System.LimitException: Query of LOB fields caused heap usage to exceed limit

So I am trying to clone ~11000 attachments over to new object records. I have developed the code below with help from this community and I have tested it on a sandbox with 3 attachments to move over. Works great. But when I deploy it and trigger the code, I get the error below:

FATAL_ERROR System.LimitException: Query of LOB fields caused heap usage to exceed limit.

The Code:

trigger SecondStepClone on Opportunity (After update) {
    List<Attachment> ToInsertList = new List<Attachment>();  
    Attachment tempatt; 

    Map<Id, Id> newParentMap = new Map<Id, Id>();

    for(Opportunity curr: [SELECT ID, Selection_Record__c 
                            FROM Opportunity 
                            WHERE Selection_Record__c !='' AND (RecordTypeID = '012j0000000A8g3' 
                            OR RecordTypeID = '012j00000000Bvo' 
                            OR RecordTypeID = '012j00000000Bvj'
                            OR RecordTypeId = '012j000000114KI')]) {

        newParentMap.put(curr.Id, curr.Selection_Record__c);       

    List<Attachment> attlist = [SELECT id, parentid, body, name 
                                FROM Attachment 
                                WHERE parentid 
                                IN: newParentMap.keyset()];  

    for(Attachment temp: attlist){

    insert ToInsertList;

Not sure what next steps would be to prevent the heap size from being exceeded. Help would be much appreciated.

Best Answer

There's no need to clone the records, since you can just reset the id field by assigning null.

for(Attachment temp: attList) {
    temp.Id = null;
    temp.ParentId = newParentMap.get(temp.ParentId);
insert attList;