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Trigger-bulkification is a Salesforce technique. Using trigger-bulkification, triggers can handle creation or updates of more than one record at a time. This technique helps avoid hitting governor limits on your triggers during a mass creation or update. Bulkifying means grouping up all your data manipulation operations into as few operations as possible. In practical terms, this usually means moving such operations outside of for-loops. For more information about bulkifying triggers, see Salesforce help and http://blog.jeffdouglas.com/2009/04/20/writing-bulk-triggers-for-salesforce/.

Performing data-manipulation (DML) operations in triggers that run after record inserts or updates can cause trigger looping. For example, a task object has a trigger which modifies a lead, and a lead object has a trigger that modifies a task. The task's trigger initiates the lead's trigger, and then the lead's trigger initiates the task's trigger, and so on. This situation results in an endless loop of trigger execution.

To avoid this situation, wherever possible, use triggers that run before update or insert. DML is not allowed in triggers that run before update or insert.

If you cannot run your triggers before insert or update, use the following code. The code protects your triggers from firing repeatedly by checking whether they are already executing:

public Class CheckRecursive{
    private static boolean run = true;
    public static boolean runOnce(){
        if (run) {
            run = false;
            return true;
        } else {
            return run;
        }
    }
}

The runOnce method only returns true the first time the trigger runs in a single execution context. If you check the value before running your trigger, you will prevent trigger looping.

trigger MyTrigger on Task (after update) {
 
    // Exit if we're being called recursively
    if(!checkRecursive.runOnce()) return;
    
    // Do stuff!
}

For more information about avoiding trigger looping, see Salesforce help.

Sometimes you might want to know the number of tasks related to a specific Salesforce object, for example, a contact or lead. You can use this number in reports later.

The easy, but not recommended, way to count tasks is to use a trigger. The trigger updates the count in a custom field on the related record. This method is likely to cause concurrent editing issues.

Instead we recommend you use an embedded Visualforce page to view a count of related task records.

To create a Visualforce page and embed it in the page layout, perform the following steps:

1. Create an Apex Class which counts the task records relating to the object.
   The following example code counts tasks related to contacts. Modify this code to count tasks related to other Salesforce objects such as leads or accounts.

   Code Block
   language java title TaskCountController class to count tasks linenumbers true
   public class TaskCountController { private Contact currentContact; public TaskCountController (ApexPages.StandardController base) { currentContact = (Contact) base.GetRecord (); } public Integer GetNumberOfAssociatedTasks () { return [SELECT COUNT () FROM Task WHERE WhoId = :currentContact.Id ]; } }

   
   

2. Create the Visualforce page and include the class you create in step 1.
   The following example Visualforce page uses the code in the TaskCountController class.

   Code Block
   language xml title Visualforce page to count tasks linenumbers true
   <apex:page standardcontroller="Contact" extensions="TaskCountController"> <apex:outputLabel for="taskCount" style="font-weight: bold;color: #4a4a56">Task count</apex:outputLabel>&nbsp; <apex:outputText id="taskCount" value="{!NumberOfAssociatedTasks}"/> </apex:page>

   
   

3. Embed the Visualforce page you create in step 2 in your object's page layout. Set the height of the Visualforce component to 14px so the field looks like a normal row on the page.