Write a Salesforce Batch Apex class to process large datasets in chunks with start, execute, and finish methods

In-depth guide

Steps

1. Implement the Database.Batchable<SObject> interface with three methods: start(), execute(), and finish()
2. In start(), return a Database.QueryLocator using Database.getQueryLocator('SELECT Id, ... FROM Object WHERE ...') to let the platform paginate up to 50 million records
3. In execute(Database.BatchableContext bc, List<SObject> scope), process the current batch chunk; the default and maximum batch size is 200 records per execute call
4. In finish(Database.BatchableContext bc), perform post-processing such as sending a summary email or enqueuing a follow-up job using AsyncApexJob query on bc.getJobId()
5. Submit the batch using Database.executeBatch(new MyBatch(), batchSize), specifying a smaller batch size (e.g., 10–50) if the execute method makes callouts or performs complex processing
6. Monitor job progress by querying AsyncApexJob where Id = :bc.getJobId() to check JobItemsProcessed, TotalJobItems, and Status fields