i'm getting this error: Too many query rows: 50001

public without sharing class OpportunityPipelineChangeProcessing {
public static Date TodaysDate = system.today();
    public static void OCP(){
         // Pull in all Open Opportunity records
        Map<Id,Opportunity> mapOpportunity= new Map<Id, Opportunity>
        ([Select Id, CurrencyIsoCode, IsClosed, StageName, CloseDate, Amount, OwnerId, OpportunityPipelineChangeId__c, OpportunityPipelineChanged__c  from Opportunity where IsClosed = False or OpportunityPipelineChanged__c = True]);
       
        // Pull in all prior Pipeline Change records
        Map<Id, Id> mapPC = new Map<Id, Id>();
        Set<Id>     setPC = new Set<Id>();
        for (Opportunity z: mapOpportunity.values()){
            if(z.OpportunityPipelineChangeId__c != Null){
             mapPC.put(z.OpportunityPipelineChangeId__c, z.id);
             setPC.add(z.OpportunityPipelineChangeId__c);  
            }
        }
        Map<Id,OpportunityPipeline_Change__c> mapOpportunityPipeline_Change = new Map<Id, OpportunityPipeline_Change__c>
        ([Select Id, Opportunity__c, Amount_After__c, Amount_Prior__c, Close_Date_After__c, Close_Date_Prior__c, Stage_After__c, Stage_Prior__c, New_Opportunity__c from OpportunityPipeline_Change__c where Id = :setPC]);       

        // Create new OpportunityPipeline Change records
        List<OpportunityPipeline_Change__c> listOpportunityPipelineChangeAdds = new List<OpportunityPipeline_Change__c>();
        for (Opportunity z: mapOpportunity.values()){
            boolean NewOpportunity = True;
            decimal PriorAmountAfter = 0.00;
            string  PriorStageAfter = Null;
            date    PriorCloseDateAfter = Null;
            OpportunityPipeline_Change__c PC = Null;
           
            if(z.OpportunityPipelineChangeId__c != Null){             
                PC = mapOpportunityPipeline_Change.get(z.OpportunityPipelineChangeId__c);
                if(PC != null){
                    NewOpportunity      = False;
                    PriorAmountAfter    = PC.Amount_After__c;
                    PriorStageAfter     = PC.Stage_AFter__c;
                    PriorCloseDateAfter = PC.Close_Date_After__c;
                } else {
                    PriorAmountAfter    = z.Amount;
                    PriorStageAfter     = z.StageName;
                    PriorCloseDateAfter = z.CloseDate;
                }
            } else {
                    PriorAmountAfter    = z.Amount;
                    PriorStageAfter     = z.StageName;
                    PriorCloseDateAfter = z.CloseDate;         
            }      
            listOpportunityPipelineChangeAdds.add(new OpportunityPipeline_Change__c(
                Amount_After__c                 = z.Amount,
                Amount_Prior__c                 = PriorAmountAfter,
                Close_Date_After__c             = z.CloseDate,
                Close_Date_Prior__c             = PriorCloseDateAfter,
                CurrencyIsoCode                 = z.CurrencyIsoCode,
                Effective_Date_Time__c          = TodaysDate,
                EffectiveDateMilliseconds__c    = System.currentTimeMillis(),
                New_Opportunity__c              = NewOpportunity,
                Opportunity__c                  = z.Id,
                Opportunity_Amount__c           = z.Amount,
                Stage_After__c                  = z.StageName,
                Stage_Prior__c                  = PriorStageAfter));
        }
       
        Insert(listOpportunityPipelineChangeAdds);
       
        // Update Opportunities and put in new OpportunityPipelineChange Id and reset OpportunityPipelineChanged__c value to False
        List<Opportunity> listOpportunityUpdates = new List<Opportunity>();
        for (OpportunityPipeline_Change__c z: listOpportunityPipelineChangeAdds){
            listOpportunityUpdates.add(new Opportunity(
                id                             = z.opportunity__c,
                OpportunityPipelineChangeId__c = z.id,
                OpportunityPipelineChanged__c  = false));
        }
        Update(listOpportunityUpdates); 

}
}

Thanks
kumar