Batch delete articles and topics via dev console.

BatchDeleteArticles.cls

public with sharing class BatchDeleteArticles implements Database.batchable<SObject>,Database.allowscallouts,Database.Stateful{
    private String configId;

    public BatchDeleteArticles (String configId) {
      this.configId = configId;
    }

    public BatchDeleteArticles () {

    }

    public Iterable<SObject> start(Database.batchableContext batchableContext) {

        String kbObject = 'knowledge__kav'; //MigrationHelper.getKnowledgeObject(configId);
        List<SObject> dral = Database.query('select id, KnowledgeArticleId, publishstatus from ' + kbObject + ' where publishstatus = \'Draft\'');
        List<SObject> onal = Database.query('select id, KnowledgeArticleId, publishstatus from ' + kbObject + ' where publishstatus = \'Online\'');
  	   	List<SObject> al = new List<SObject>();
        al.addall(dral);
        al.addall(onal);
        return al;

    }

    public void execute(Database.BatchableContext batchableContext, List<SObject> al)  {
        List<SObject> dral = new List<SObject>();
        List<SObject> onal = new List<SObject>();

        for (SObject a:al){
            if ((String)a.get('PublishStatus') == 'Draft'){
                KbManagement.PublishingService.deleteDraftArticle((String)a.get('KnowledgeArticleId'));
            }
            if ((String)a.get('PublishStatus') == 'Online'){
                KbManagement.PublishingService.archiveOnlineArticle((String)a.get('KnowledgeArticleId'),null);
    			KbManagement.PublishingService.deleteArchivedArticle((String)a.get('KnowledgeArticleId'));
            }
        }

    }

    public void finish(Database.BatchableContext bc) {

    }
}