ApexSpeedExperiment_2.cls

/*
    Speed Test - Filtering records using List<Id> versus List<sObject> in SOQL
    Author: 0to1Code.Com
*/
public class ApexSpeedExperiment_2{
    
    //Experiment 1 : Querying records using list of sObject with Id fields
    public static void runExperiment1(){
        //This Query only includes only Id field
        List<Lead> leadLst = [select id from lead];
        
        system.debug('CPU Limit Consumption Start: '+Limits.getCPUtime());
        
        List<Lead> reQueryingLeads = [select id,name,company from lead where id in: leadLst];
        
        system.debug('CPU Limit Consumption End: '+Limits.getCPUtime());
    }
    
    
    //Experiment 2 : Querying records using list of Ids
    public static void runExperiment2(){
        List<Lead> leadLst = [select id from lead];
        
        List<Id> lIds = new List<Id>();
        for( lead l : leadLst){
            lIds.add(l.id);
        }
        
        /*
        EDIT: 1 Jan 2019
        We can use this to get ids of records instead of using above for loop
        Suggested by ifernandosousa
        
        Set<Id> lIds = (new Map(leadLst)).keySet();        
        */
        
        system.debug('CPU Limit Consumption Start: '+Limits.getCPUtime());
        
        List<Lead> reQueryingLeads = [select id,name,company from lead where id in: lIds];
        
        system.debug('CPU Limit Consumption End: '+Limits.getCPUtime());
    }
    
    //Experiment 3 : Querying records using list of sObject with more fields
    public static void runExperiment3(){
        //This Query only includes more than one field
        List<Lead> leadLst = [select id,name,company, Address, Industry, AnnualRevenue from lead];
        
        system.debug('CPU Limit Consumption Start: '+Limits.getCPUtime());
        
        List<Lead> reQueryingLeads = [select id,name,company from lead where id in: leadLst];
        
        system.debug('CPU Limit Consumption End: '+Limits.getCPUtime());
    }
}