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Gowthami R 8Gowthami R 8 

When do we use batch class?

Hi everyone,
Can anyone explain me why do we use batch class? Why do we use batch classess,In which scenario does the batch appear?
Thanks in Advance,
 
NagendraNagendra (Salesforce Developers) 
Hi Gowthami,

Batch Apex: Batch Apex is exposed as an interface that must be implemented by the developer. Batch jobs can be programmatically invoked at runtime using Apex.

Need of Batch Apex: - As you, all might know about the sales force governor limits on its data. When you want to fetch thousands of records or fire DML on thousands of rows on objects it is very complex in Salesforce and it does not allow you to operate on more than a certain number of records which satisfy the Governor limits.

But for medium to large enterprises, it is essential to manage thousands of records every day. Adding/editing/deleting them when needed.
Salesforce has come up with a powerful concept called Batch Apex. Batch Apex allows you to handle more number of records and manipulates them by using a specific syntax.

We have to create a global apex class which extends Database.Batchable Interface because of which the sales force compiler will know, this class incorporates batch jobs. Below is a sample class which is designed to delete all the records of Account object (Lets say your organization contains more than 50 thousand records and you want to mass delete all of them).

Here is the real-time scenario:

If you have a business logic to send an email 180 days before the Contract expiration, we want to notify the User that the Contract is going to expire.

If we have only 180 days is the criteria then we can achieve this using Time based Workflow. But for this we need to touch the records as least once.

If we have additional criteria along with 180 days less than and also should work for all existing records as well then we will use some concept which should run the background where there is no need of user modifying the record.

In this situation, we will go with Batch Apex, which will run everyday night and check all the Contracts which are expiring in next 180 days and send an email to the Contact Person.

Sample Batch Apex

1) Start method is automatically called at the beginning of the apex job. This method will collect record or objects on which the operation should be performed. These records are divided into subtasks & pass those to execute method.

2) Execute Method performs an operation which we want to perform on the records fetched from start method.

3) Finish method executes after all batches are processed. Use this method to send confirmation email notifications.
global class deleteAccounts implements Database.Batchable{

global final String Query;

global deleteAccounts(String q){
Query=q;
}

global Database.QueryLocator start(Database.BatchableContext BC){
return Database.getQueryLocator(query);
}

global void execute(Database.BatchableContext BC,List scope){
List <Account> lstAccount = new list<Account>();
for(Sobject s : scope){
 Account a = (Account)s;
lstAccount.add(a);
}
Delete lstAccount;
}

global void finish(Database.BatchableContext BC){
                //Send an email to the User after your batch completes

                Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();

String[] toAddresses = new String[] {‘sforce2009@gmail.com’};

mail.setToAddresses(toAddresses);

mail.setSubject('Apex Batch Job is done‘);

mail.setPlainTextBody('The batch Apex job processed ');

Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });

}

}
For more information please check with below link. Hope this helps.

Please mark this as solved if it's resolved so that it gets removed from the unanswered queue which results in helping others who are encountering a similar issue.

Thanks,
Nagendra
Amit Chaudhary 8Amit Chaudhary 8

Batch Apex
A Batch class allows you to define a single job that can be broken up into manageable chunks that will be processed separately.
http://amitsalesforce.blogspot.com/2016/02/batch-apex-in-salesforce-test-class-for.html

When to use Batch Apex
One example is if you need to make a field update to every Account in your organization. If you have 10,001 Account records in your org, this is impossible without some way of breaking it up. So in the start() method, you define the query you're going to use in this batch context: 'select Id from Account'. Then the execute() method runs, but only receives a relatively short list of records (default 200). Within the execute(), everything runs in its own transactional context, which means almost all of the governor limits only apply to that block. Thus each time execute() is run, you are allowed 150 queries and 50,000 DML rows and so on. When that execute() is complete, a new one is instantiated with the next group of 200 Accounts, with a brand new set of governor limits. Finally the finish() method wraps up any loose ends as necessary, like sending a status email.


Sample Batch Apex
1) Start method is automatically called at the beginning of the apex job. This method will collect record or objects on which the operation should be performed. These record are divided into subtasks & passes those to execute method.
2) Execute Method performs operation which we want to perform on the records fetched from start method.
3) Finish method executes after all batches are processed. Use this method to send confirmation email notifications.
global class AccountUpdateBatchJob implements Database.Batchable<sObject> 
{
    global Database.QueryLocator start(Database.BatchableContext BC) 
    {
        String query = 'SELECT Id,Name FROM Account';
        
        return Database.getQueryLocator(query);
    }
    global void execute(Database.BatchableContext BC, List<Account> scope) 
    {
        for(Account a : scope)
        {
            a.Name = a.Name + 'Updated by Batch job';
        }
        update scope;
    }
    global void finish(Database.BatchableContext BC) {
    }
}

Calling on Batch Apex

            AccountUpdateBatchJob obj = new AccountUpdateBatchJob();
            DataBase.executeBatch(obj); 

Limits in Batch Apex
1) Up to five queued or active batch jobs are allowed for Apex
2) Cursor limits for different Force.com features are tracked separately. For example, you can have 50 Apex query cursors, 50 batch cursors, and 50 Visualforce cursors open at the same time.
3) A maximum of 50 million records can be returned in the Database.QueryLocator object. If more than 50 million records are returned, the batch job is immediately terminated and marked as Failed
4) If the start method returns a QueryLocator, the optional scope parameter of Database.executeBatch can have a maximum value of 2,000. If set to a higher value, Salesforce chunks the records returned by the QueryLocator into smaller batches of up to 2,000 records. If the start method returns an iterable, the scope parameter value has no upper limit; however, if you use a very high number, you may run into other limits.
5) If no size is specified with the optional scope parameter of Database.executeBatch, Salesforce chunks the records returned by the start method into batches of 200, and then passes each batch to the execute method.Apex governor limits are reset for each execution of execute.
6) The start, execute, and finish methods can implement up to 10 callouts each
7) The maximum number of batch executions is 250,000 per 24 hours
8) Only one batch Apex job's start method can run at a time in an organization. Batch jobs that haven’t started yet remain in the queue until they're started. Note that this limit doesn’t cause any batch job to fail and execute methods of batch Apex jobs still run in parallel if more than one job is running

Let us know if this will help you
 
NILESH RAJ 20NILESH RAJ 20
Batch apex covers the entire set of records that needs to be processed and divide it into small manageable chunks. This is a very powerful method of executing millions of records like in data cleaning or archiving records which otherwise would hit the governor limit in normal DML operation.
For complete detail on batch apex you can check : https://sfdcwisdom.com/batch-apex-in-salesforce/
Suraj Tripathi 47Suraj Tripathi 47
Hi Gowthami,

1)Batch Apex is used to run large jobs that would exceed
normal processing limits.
2)Using Batch Apex, you can process records asynchronously in batches to stay within platform limits. 
You can take references from this link for more information.
https://trailhead.salesforce.com/content/learn/modules/asynchronous_apex/async_apex_batch

If you find your Solution then mark this as the best answer. 

Thank you!

Regards 
Suraj Tripathi