We have recently started using Parent/Child Account relationships in Salesforce, and have a filtered Roll-Up field to sum live open Opps with Accounts. We wanted to be able to sum that field on all child Accounts to the Parent level, so I found an Apex Class and Trigger on line that seemed like it would work.

However, every time an edit is made to any Account record in Salesforce, I receive a gov limit warning:

"Approaching limit for non-selective query against large object type (more than 100000 rows). Current size is approximately 94107 rows. When the limit is reached, the query will fail. "

I know this is because it's querying all Accounts (since we have approximately 94,100 Account records) every time it runs, but I am not yet comfortable enough with the Apex language to know what I need to do to prevent it from querying every Account record every time.

Below is the Class and the Trigger we have. Any help is greatly appreciated as I learn by trial and error.

CLASS:

public class RollUpSummaryUtility {
     
    //the following class will be used to house the field names
    //and desired operations
    public class fieldDefinition {
        public String operation {get;set;}
        public String childField {get;set;}
        public String parentField {get;set;}
         
        public fieldDefinition (String o, String c, String p) {
            operation = o;
            childField = c;
            parentField = p;
        }
    }
     
    public static void rollUpTrigger(list<fieldDefinition> fieldDefinitions,
    list<sObject> records, String childObject, String childParentLookupField,
    String parentObject, String queryFilter) {
         
        //Limit the size of list by using Sets which do not contain duplicate
        //elements prevents hitting governor limits
        set<Id> parentIds = new set<Id>();
         
        for(sObject s : records) {
            parentIds.add((Id)s.get(childParentLookupField));
        }
         
        //populate query text strings to be used in child aggregrator and
        //parent value assignment
        String fieldsToAggregate = '';
        String parentFields = '';
         
        for(fieldDefinition d : fieldDefinitions) {
            fieldsToAggregate += d.operation + '(' + d.childField + ') ' +
            ', ';
            parentFields += d.parentField + ', ';
        }
         
        //Using dynamic SOQL with aggergate results to populate parentValueMap
        String aggregateQuery = 'Select ' + fieldsToAggregate +
        childParentLookupField + ' from ' + childObject + ' where  ' +
        childParentLookupField + ' IN :parentIds ' + queryFilter + ' ' +
        ' group by ' + childParentLookupField;
         
        //Map will contain one parent record Id per one aggregate object
        map<Id, AggregateResult> parentValueMap =
        new map <Id, AggregateResult>();
         
        for(AggregateResult q : Database.query(aggregateQuery)){
            parentValueMap.put((Id)q.get(childParentLookupField), q);
        }
         
        //list of parent object records to update
        list<sObject> parentsToUpdate = new list<sObject>();
         
        String parentQuery = 'select ' + parentFields + ' Id ' +
         ' from ' + parentObject + ' where Id IN :parentIds';
         
        //for each affected parent object, retrieve aggregate results and
        //for each field definition add aggregate value to parent field
        for(sObject s : Database.query(parentQuery)) {
             
            Integer row = 0; //row counter reset for every parent record
            for(fieldDefinition d : fieldDefinitions) {
                String field = 'expr' + row.format();
                AggregateResult r = parentValueMap.get(s.Id);
                //r will be null if no records exist
                //(e.g. last record deleted)
                if(r != null) {
                    Decimal value = ((Decimal)r.get(field) == null ) ? 0 :
                        (Decimal)r.get(field);
                    s.put(d.parentField, value);
                } else {
                    s.put(d.parentField, 0);
                }
                row += 1; //plus 1 for every field definition after first
            }
            parentsToUpdate.add(s);
        }
         
        //if parent records exist, perform update of all parent records
        //with a single DML statement
        if(parentsToUpdate.Size() > 0) {
            update parentsToUpdate;
        }
         
    }
 
}

 TRIGGER:

trigger CustomeParentAccountRollUpOpenOpps on Account (after delete, after update) {
     
    if(trigger.isUpdate){
         
        list<RollUpSummaryUtility.fieldDefinition> fieldDefinitions =
        new list<RollUpSummaryUtility.fieldDefinition> {
            new RollUpSummaryUtility.fieldDefinition('SUM', 'Live_Open_Opp__c',
            'Child_Account_Open_Opp_Dollars_Trigger__c')
        };
         
        RollUpSummaryUtility.rollUpTrigger(fieldDefinitions, trigger.new,
        'Account', 'Parent_Account_Custom__c', 'Account', '');
         
    }
     
    if(trigger.isDelete){
         
        list<RollUpSummaryUtility.fieldDefinition> fieldDefinitions =
        new list<RollUpSummaryUtility.fieldDefinition> {
            new RollUpSummaryUtility.fieldDefinition('SUM', 'Live_Open_Opp__c',
            'Child_Account_Open_Opp_Dollars_Trigger__c')
        };
         
        RollUpSummaryUtility.rollUpTrigger(fieldDefinitions, trigger.old,
        'Account', 'Parent_Account_Custom__c', 'Account', '');
         
    }
     
}