REQUEST_RUNNING_TOO_LONG :Your request was running for too long, and has been stopped

Question

I have created a Batch which is supposed to pull Completed tasks and Reopen them. It's a simple implementation (code attached), but what i observe is the Query is taking too long and ultimately aborts the batch.

I am not able to figure out what's causing this query to fail/take too long. Any help is appreciated!

public class ReopenReferralTasksBatch implements Database.Batchable<sObject>,Database.Stateful {

    public Database.QueryLocator start(Database.BatchableContext BC){
        String TASK_QUERY = 'SELECT Status FROM Task WHERE Status = \'Completed\' AND Type = \'Referral Enquiry\'';
        TASK_QUERY += ' AND Referral_Reopen_Date__c = TODAY';
        return Database.getQueryLocator(TASK_QUERY);
    }
    public void execute(Database.BatchableContext BC, List<Task> tasksToBeReOpened){
        List<Task> reOpenedTasks = new List<Task>();
        for(Task task : tasksToBeReOpened){
            task.Status = 'Open';
            reOpenedTasks.add(task);
        }
        
        if(reOpenedTasks.size()>0){
            Database.SaveResult[] saveResultList = database.update(reOpenedTasks);
            Integer index = 0;
            for(Database.SaveResult svrslt : saveResultList){
                if(!svrslt.isSuccess()){
                    String errMsg = svrslt.getErrors()[0].getMessage();
                    errorMap.put(reOpenedTasks[index].Id, errMsg);
                }
                else{
                    String sucMsg = baseURL + '/' + reOpenedTasks[index].Id;
                    successMap.put(reOpenedTasks[index].Id, sucMsg);
                    IdToSObjectMap.put(reOpenedTasks[index].Id, reOpenedTasks[index]);
                }
                index++;
            }
        } 
    }
    public void finish(Database.BatchableContext BC){
        WHJ_BatchMailHandler.Sendmail(IdToSObjectMap, errorMap, successMap, 'ReopenReferralTasksBatch');
    }
}

Not just that, if a run the following query in dev console, it times out:

SELECT Status,Referral_Reopen_Date__c FROM Task WHERE Status = 'Completed'

Edit: Batch Size: executing with no explicit batch size from anonymous window.

Start method is the one where this limit is exceeded.

Referral_Reopen_Date__c : is a date type field.

If i add a today clause (Referral Reopen Date = Today) in the following:

SELECT Status,Referral_Reopen_Date__c FROM Task WHERE Status = 'Completed'

It still times out on the QUERY stating: It's taking too long!

Answer 1

I just appended a clause: 'AND LastModifiedDate = LAST_N_DAYS:30' to my query and it seems not failing now. I am not really an expert on SOQL optimisation but i think this brought down the size of the chunk through which the query traverses.