Apex Loop Optimize

Question

Here is my code

// dynamic fields, the same with queried fields of Database.query(sqlStr)   
String fieldList = 'Id, Name, Number, Text__c..........'.split(',');
for(SObject sob : Database.query(sqlStr))
{
    String[] rowValues = new String[] {};
    for(Integer i = 0, j = fieldList.size(); i < j; i++)
    {
        String fieldValueStr = String.valueOf(sob.get(fieldList[i]));
        rowValues.add(fieldValueStr);
    }
    String joinedRowValues = String.join(rowValues, ' ▏');
    this.values.add(joinedRowValues); // values is from a class property  
}

the result will be like this

"values": [   
        "00190000014IoCoAAK ▏ 00081 ▏ Super Mart ▏ ...",  
        "00190000014EoCAABK | 0008tator | Test Mart ▏ ...",
        ......................................  
],

If data is more than 5000, there will be lots of loop, for example, we have 30 fields, 5000 records, loop will be 30*5000. Too many loop will cause CPU timeout.
How to reduce this loop and also get the same result?

Answer 1

Considering the numbers you provided, I really don't think timing is an issue here. I've wrote the following code to simulate;

String[] l = new String[]{};
for(Integer i=0; i<5000; i++){
    String[] l2 = new String[]{};
    for(Integer j=0; j<30; j++){
        l2.add('test');
    }
    l.add(String.join(l2, '|'));
}
system.debug(l.size());

If I execute this piece anonymously, the Maximum CPU time limit is always below 1000 out of 10000. Of course, depending on the growth of the number of records or fields, or depending on other parts of your code, it could be a problem. But just considering the givens, I don't think it is right now.