How To Invoke Batch Apex From Another Batch Apex In Salesforce

How is it possible?

There are two ways in salesforce which are used to call the batch class from another batch class are:

• Using Queueable Apex
• Using the Finish method of Batch class.

Using this way, you can create the chaining between the batches.

Note: If you call the batch class from start or execute methods then Salesforce throws the below error:
System.AsyncException: Database.executeBatch cannot be called from a batch start, batch execute, or future method.

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While calling batch from the start method there is an error:

Same error while calling from execute method of batch:

Here is the complete definition of error message:
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There are two solutions for this error:

1. Using Queueable Apex:

2. Using Finish Method of Batch Class:

Batch Class Example:

global class BatchAccountUpdate implements Database.Batchable<sObject>, Database.Stateful, Database.AllowsCallouts {
String query = 'Select Name from Account WHERE Name != null AND (Name = \'Sapna Company\' OR Name = \'Sapna\') ';
global Database.QueryLocator start(Database.BatchableContext bc) {
// collect the batches of records or objects to be passed to execute
return Database.getQueryLocator(query);
}

global void execute(Database.BatchableContext bc, List<Account> records){
// process each batch of records
for(Account acc : records){
acc.Name = acc.Name + ' - Updated';
}
update records;
}

global void finish(Database.BatchableContext bc){
// execute any post-processing operations
Note: We are calling Batch from Finish Method of Second batch.
BatchUpdateAccountRelatedContacts b = new BatchUpdateAccountRelatedContacts();
Database.executeBatch(b, 200);
}
}

Calling from Schedule Class:

global class ScheduleBatchAccountUpdate implements Schedulable {
global void execute(SchedulableContext sc) {
BatchAccountUpdate b = new BatchAccountUpdate();
database.executebatch(b);
}
}

Second Batch:

global class BatchUpdateAccountRelatedContacts implements Database.Batchable<sObject>, Database.Stateful, Database.AllowsCallouts {
String query = 'Select FirstName, LastName, Email, Status__c from Contact WHERE
FirstName != null AND LastName != null AND AccountId != null';
global Database.QueryLocator start(Database.BatchableContext bc) {
// collect the batches of records or objects to be passed to execute
Note: Calling Queueable job for calling the next batchfor chaining.
System.enqueueJob(new ExecuteBatchQueueableJob());
return Database.getQueryLocator(query);
}
global void execute(Database.BatchableContext bc, List<Contact> records){
// process each batch of records
for(Contact con : records){
con.Status__c = 'Discovery Call Complete';
}
update records;
}
global void finish(Database.BatchableContext bc){
// execute any post-processing operations
}
}

Queueable Apex:

public class ExecuteBatchQueueableJob implements Queueable {
public void execute(QueueableContext context) {
try{
BatchCalledThroughQueueable b = new BatchCalledThroughQueueable();
Database.executeBatch(b, 200);
}catch(Exception e){
System.debug('@@@ Error Message : '+e.getMessage());
}
}
}

Third Batch:

global class BatchCalledThroughQueueable implements Database.Batchable<sObject>, Database.Stateful, Database.AllowsCallouts {
String query = 'Select FirstName, LastName, Email, Status, Title from Lead WHERE FirstName != null AND LastName != null';
global Database.QueryLocator start(Database.BatchableContext bc) {
// collect the batches of records or objects to be passed to execute
return Database.getQueryLocator(query);
}
global void execute(Database.BatchableContext bc, List<Lead> records){
// process each batch of records
for(Lead ld : records){
ld.Title = ld.FirstName + ' - ' + ld.LastName;
}
update records;
}
global void finish(Database.BatchableContext bc){
// execute any post-processing operations
}
}

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