delete records from multiple objects via apex batch class

Question

I have a requirement for a process that would delete qualified records from multiple objects. There are about 5 objects and criteria for deletion is the same for all objects. I want to do all of it in one batch class, possibly by iterating through each object, adding records for deletion to one common list and then perfom a delete. Is this possible? Can someone please help with the syntax?

Thank you!

Answer 1

You can combine up to 10 types of SObject in one list for DML as long as they are grouped by type. See this post by Jesse Altman for more color on that.

You can accomplish what you are looking for by using an Iterable. Take a look here for a good example of how to use an Iterable in a batch (at the bottom). You will want to iterate over a List<SObject>. In your constructor, add your various queries one by one to this list.

Rough example:

global class CustomIterable implements Iterator<SObject>
{
    final List<SObject> records;
    global CustomIterable()
    {
        records = new List<SObject>();
        records.addAll((List<SObject>)[SELECT Id FROM Account]); // WHERE...
        records.addAll((List<SObject>)[SELECT Id FROM Contact]); // WHERE...
        records.addAll(Database.query('SELECT Id FROM Opportunity')); // WHERE...
    }

    // rest of implementation
}

This general approach should get you started.

Answer 2

Here's how I decided to implement my requirement. Still need to test it, but high level seems to be working:

global class DeleteRecords implements Database.Batchable<string>, Database.Stateful  {
global boolean bReRun = false; //will be used to determine if batch has to re-run in case there are more that 10K of records
global Iterable<string> start(Database.BatchableContext ctx) {
    return new list<String> { 'object1', 'object2', 'object3','object4','object5'}; //list of strings with my object names
}
global void execute(Database.BatchableContext ctx, list<string> lstsObjectName) {
    list<sObject> lstDeleteRecords = new list<sObject>();
    for(string strObjectName : lstsObjectName) {
        for(sObject objsObject : database.query('Select Id from ' + strObjectName + ' where for_delete__c = TRUE')) {
            if(lstDeleteRecords.size() < 9998)
                lstDeleteRecords.add(objsObject);
            else {
                bReRun = true;
                break;
            }
        }
    }
    lstDeleteRecords.sort();
    delete lstDeleteRecords;
}
global void finish(Database.BatchableContext ctx) {
    if(bReRun) {
         Database.executebatch(new DeleteRecords());
    }
}

}

Answer 3

Another option is to call batches in chain, so you can get advantage of Database.queryLocator that is able to return more records than Iterator.

On each chain you can query the object you want to remove and delete it. You would be able to set different scopeSize for each one as well if this is required. Maybe objectA is more complex than objectB

public with sharing class MyBatch implements Database.Batchable<sObject>, Database.Stateful
{
    private Integer currentChain;

    private Integer scopeSize;

    public MyBatch()
    {
        currentChain = 1;
    }

    public MyBatch(Integer chain)
    {
        currentChain = chain;
    }

    public Database.QueryLocator start(Database.BatchableContext BC)
    {
        String qry;

        if(currentChain == 1)
        {
            qry = 'Select Id From ObjectA__c';
        }
        else(currentChain == 2)
        {
            qry = 'Select Id From ObjectB__c';
        }

        return Database.getQueryLocator(qry);
    }

    public void execute(Database.BatchableContext BC, List<sObject> scope)
    {
        delete scope;       
    }

    public void finish(Database.BatchableContext BC)
    {
        if(currentChain == 1)
        {
            MyBatch mb = new MyBatch(currentChain++);
            Database.execute(mb, scopeSize);
        }
        else(currentChain == 2)
        {
            sendEmail();
        }
    }
}

Answer 4

Replace your start with the following:

global Iterable<sObject> start(Database.BatchableContext bc) {

        // Database.getQueryLocator([Select Name  from blah LIMIT 10000]);
        List<sObject> lstUPQs = [select Id from Account where ... LIMIT 5000];
        List<sObject> lstJRs = [select Id from Contact where ... LIMIT 5000];
        
        List<sObject> lstAll = new List<sObject>();
        lstAll.addAll(lstUPQs);
        lstAll.addAll(lstJRs);
        
        return lstAll;
    }

 global void execute(Database.BatchableContext bc, List<sObject> scope){
       
        delete scope;
    }