How can we keep the global variable at Apex Batch

Question

I have a use case to run sequence of Batch to execute my logic. There I need to have a way to start the Batch and terminate it, So for that I keep a global variable to store the records and according to the record I was start the Batch in sequence. I will share my code below and if you have any idea please share with me to overcome this issue,

I am thinking that when we start the sequence batch their might be the global variable reset.

global class Main_BATCH implements Database.Batchable<SObject>, Database.Stateful {

    global String query;
    public static List<Object_Rule__mdt> ObjectAndFieldsRule;

    global Main_BATCH() {

        ObjectAndFieldsRule = new List<Object_Rule__mdt>();

        if (ObjectAndFieldsRule.size() == 0) {
            ObjectAndFieldsRule = [
                    SELECT soco__Action__c, soco__Order__c, soco__SObject__c, 
(SELECT soco__Action__c, soco__Field_Name__c, Object_Rule__c FROM 
Field_Rules__r)
                FROM Object_Rule__mdt
                ORDER BY soco__Order__c
        ];
    }

    this.query = 'Construct query according to the meta data Master and Child records'
    }

    global Database.QueryLocator start(Database.BatchableContext bc) {
        return Database.getQueryLocator(this.query);
    }

    global void execute(Database.BatchableContext BC, List<SObject> sobjects){
    try {
            batchJobId = BC.getJobId();
            'Do the logic'
        } catch (Exception e) {

        }
    }

    global void finish(Database.BatchableContext bc) {

        Main_BATCH anonimizationMainBATCH = new Main_BATCH();
        ObjectAndFieldsRule.remove(0);
        if (ObjectAndFieldsRule.size() > 0) {
            Database.executeBatch(anonimizationMainBATCH, 200);
        }
    }
}

When I run the above Batch it act as an infinite Batch with the first meta data record.

Answer 1

Static variables are not stored in an object's state, and therefore won't be retained across transactions in your batch. You will need to make the variable an instance variable:

public List<Object_Rule__mdt> ObjectAndFieldsRule;

---

In addition, you need to use the same instance of your batch when chaining:

Database.executeBatch(this, 200);

This will "keep your place" with the state you had previously.