Can Database.executeBatch be called from a Queueable started by System.enqueueJob?

Question

I'm aware that you can't call Database.executeBatch from the execute method of an already running Batchable.

But can Database.executeBatch be called from a Queueable running via System.enqueueJob? I'm asking because I'm looking to but an asynchronous layer on top of some code that is already using batchables.

(This Can Queueable solve "Future method cannot be called from a future or batch method"? confirms this works the opposite way round i.e. a Queueable can be called from a Batchable.)

PS

Interestingly, while Batchable -> Batchable isn't supported, Batchable -> Queueable -> Batchable is, so the Queueable insulates the pair of Batchables from that restriction.

Answer 1

Yes, you can do that.

This is my batch class

public class BatchableDemo implements Database.Batchable<sObject>{
    
    public Database.QueryLocator start(Database.BatchableContext bc) {
        return Database.getQueryLocator('Select id from Account');
    }
    public void execute(Database.BatchableContext bc, List<Account> records){
        // process each batch of records
        system.debug('In batch');
    }
    public void finish(Database.BatchableContext bc){
        // execute any post-processing operations
    }
    
}

This is the queueable class.

public class QueueableDemo implements Queueable {
    public static void execute(QueueableContext qc){
        Database.executeBatch(new BatchableDemo());
        System.debug('batch started');
    }
}

This is the code I ran from the anonymous window.

System.enqueueJob(new QueueableDemo());

Output

Queueable job log

Batch Job log

All logs list