Database.Stateful Usecases

Database.Stateful in Apex

Normally, Batch Apex doesn’t keep variable values between execute runs, after each excute teh variable will be reset

If you need to retain the value across executes, use the Database.Stateful interface.

Example

global class MyBatchClass 
    // implement the Stateful
    implements Database.Batchable<SObject>, Database.Stateful {

    // let's say we need to calculate the count of records processes
    global Integer totalProcessed = 0;

    global Database.QueryLocator start(Database.BatchableContext BC) {
        return Database.getQueryLocator([SELECT Id FROM Account]);
    }

    global void execute(Database.BatchableContext BC, List<Account> scope) {
        // Add current count to total
        totalProcessed += scope.size();
    }

    global void finish(Database.BatchableContext BC) {
        // Logs total records processed across all batches
        System.debug('Total Processed: ' + totalProcessed);
    }
}