bulkifying trigger

Question

I am trying to bulkify my trigger and looking for help looking for help. It works fine as it is for a single record but need to ensure it works in bulk, so need to bulkify it but not sure how.

Also, I will appreciate if some one can help me with test class as well.

Thanks RP

trigger updateSerialList on Meter_Serial_Info__c(Before insert, Before update, Before delete){

    if(Trigger.isDelete || Trigger.isUpdate)
    {
        for (Meter_Serial_Info__c msio: trigger.old)
        {
            if(msio.Serial__c<> Null)
            {
                List<Serial_List__c> scsi = [select Maker__c,  id ,Array__c from Serial_List__c where Serial__c = : msio.Serial__c];
                if(scsi.size()>0)
                {
                    scsi[0].Array__c= Null;
                    update scsi;                    
                }
            }
        }
    }


    if(Trigger.isInsert || Trigger.isUpdate)
    {
        for (Meter_Serial_Info__c msi: trigger.new)
        {
            if(msi.Serial__c<> Null)
            {
                List<Serial_List__c> scsi = [select Maker__c, Array__c, id from Serial_List__c where Serial__c = : msi.Serial__c];
                if(scsi.size()>0)
                {
                    scsi[0].Array__c= msi.Array__c;
                    update scsi;
                    msi.Maker__c = scsi[0].Maker__c;               
                }
                else
                {
                    msi.Maker__c = 'Not Available'; 
                }
            }
        }
    }
}

Answer 1

Try this. As said above, the main points are to remove SOQL & DML statement from any loops.

trigger updateSerialList on Meter_Serial_Info__c(Before insert, Before update, Before delete) {

    if (Trigger.isDelete || Trigger.isUpdate) {

        Set<Id> serialIds = new Set<Id>();

        for (Meter_Serial_Info__c msio : Trigger.old) {

            if (msio.Serial__c != null) {

                serialIds.add(msio.Serial__c);
            }
        }

        List<Serial_List__c> serialListsToUpdate = new List<Serial_List__c>([]);

        for (Serial_List__c sl : [  SELECT
                                        Id,
                                        Array__c
                                    FROM
                                        Serial_List__c
                                    WHERE
                                        Serial__c IN : serialIds    ]) {

            sl.Array__c = null;

            serialListsToUpdate.add(sl);
        }

        if (!serialListsToUpdate.isEmpty()) {

            update serialListsToUpdate;
        }
    }

    if (Trigger.isInsert || Trigger.isUpdate) {

        Set<Id> serialIds = new Set<Id>();

        for (Meter_Serial_Info__c msio : Trigger.old) {

            if (msio.Serial__c != null) {

                serialIds.add(msio.Serial__c);
            }
        }

        List<Serial_List__c> relatedSerialListsToUpdate = new List<Serial_List__c>([
            SELECT
                Id,
                Array__c,
                Serial__c
            FROM
                Serial_List__c
            WHERE
                Serial__c IN : serialIds
        ]);

        List<Serial_List__c> serialListsToUpdate = new List<Serial_List__c>();

        for (Meter_Serial_Info__c msi : Trigger.new) {

            if (serialIds.contains(msi.Serial__c)) {

                for (Serial_List__c sl : relatedSerialListsToUpdate) {

                if (sl.Serial__c == msi.Serial__c) {

                    sl.Array__c = msi.Arry__c;
                    serialListsToUpdate.add(sl);

                    msi.Maker__c = sl.Maker__c;
                }
            }   

            } else {

                msi.Maker__c = 'Not Available';
            }
        }

        if (!serialListsToUpdate.isEmpty()) {

            update serialListsToUpdate;
        }
    }
}

Answer 2

The first key to Bulkification is removing SOQL and DML from loops (there are others, but this seems to be your biggest issue above). You need to leverage collections to help you do this. While I won't rewrite your trigger for you, I will give you some starting points.

In your trigger above you have a SOQL query for every record in trigger.new. So for every record that was updated, you run a SOQL query and possible do a DML statement. If you try to mass update/insert/delete some Meter_Serial_Info__c records, say a group of 200, then that means you will run 200 SOQL queries, and could possibly have 200 DML statements. The limit of SOQL queries in a single execution context is 100, so you have already doubled the limit with a relatively small mass DML.

Instead of querying for the specific Serial_List__c record in your loop. Query for all related Serial_List__c records outside of the loop and store it in a map so you can access it later.

map<Id,Serial_List__c> slMap = new map<Id,Serial_List__c>();
for(Meter_Serial_Info__c msi: trigger.new) {
    slMap.put(msi.Serial__c, null);
}
slMap.remove(null);
slMap.putAll([Select Id, Maker__c, Array__c 
               From Serial_List__c 
               Where Serial__c IN : slMap.keyset()]);

Now within your loop you can access the Serial List Object that is associated with your Meter_Serial_Info__c object.

for (Meter_Serial_Info__c msi: trigger.new) {
    if(msi.Serial__c != null) {
        slMap.get(msi.Serial__c).Array__c = msi.Array__c;
        msi.Maker__c = slMap.get(msi.Serial__c).Maker__c;               
    }
    else {
        msi.Maker__c = 'Not Available'; 
    }
}

Now notice the DML statement is no longer in the loop either. You now can call a single DML statement after all your changes have been made on your collections

for (Meter_Serial_Info__c msi: trigger.new) {
    if(msi.Serial__c != null) {
        slMap.get(msi.Serial__c).Array__c = msi.Array__c;
        msi.Maker__c = slMap.get(msi.Serial__c).Maker__c;               
    }
    else {
        msi.Maker__c = 'Not Available'; 
    }
}
***update slMap.values();***

For a update of 200 records, you would have been making 200 SOQL statements as well as possibly as many as 200 DML statements. Now you have 1 SOQL query, and 1 DML statement.

Also, check out the web, there are tons of resource son this. Here is an oldy but goody from Jeff Douglas.

http://blog.jeffdouglas.com/2009/04/20/writing-bulk-triggers-for-salesforce/

Hope that helps, and Good Luck.

Answer 3

Two important things to keep in mind for bulkifying code is to:

• Avoid SOQL inside for loops Performing DML operations such
• insert/updates on a List of objects instead of a single object inside a loop.

Move your SOQL statement outside the loop and store the data in a List/Map.

Also add the objects that need to be updated into a List and perform one update/insert/delete on this.

Please refer to this for easy to understand code examples. In any case, you need to know this to program in APEX. https://developer.salesforce.com/page/Apex_Code_Best_Practices

Answer 4

Since you are starting with Apex, it is best to start with the best practices when coding. One of them is to use Trigger framework so it is easy to plugin your custom logic inside a trigger. Examples of trigger frameworks are: https://developer.salesforce.com/page/Trigger_Frameworks_and_Apex_Trigger_Best_Practices http://developer.force.com/cookbook/recipe/trigger-pattern-for-tidy-streamlined-bulkified-triggers ...