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Kumaresan.Manickam What are the scenario to use SOQL For loops in Apex?
Dear Community,
I understand that SOQL for loops greatly helpful to avoid heap size problems while handling large set of records as it works via processing batch of request at a runtime instead of pulling whole large data at a time. But Is it best to use same SOQL for loop queries multiple times in the apex when i want to iterate a list more than once in the same context? I was concerned about performance problem if i repeat same queries more than once. Any suggestions & best practices would be very helpful
Thanks
I understand that SOQL for loops greatly helpful to avoid heap size problems while handling large set of records as it works via processing batch of request at a runtime instead of pulling whole large data at a time. But Is it best to use same SOQL for loop queries multiple times in the apex when i want to iterate a list more than once in the same context? I was concerned about performance problem if i repeat same queries more than once. Any suggestions & best practices would be very helpful
Thanks
If you get all the records of an object through SOQL in a List then you can you iterate a list more than once in the same context. There is no performance problem
to repeat the same queries more than once.
Attachment[] records = [SELECT Body FROM Attachment];
for(Attachment record: records) {
record.Body = encrypt(record.Body);
}
update records;
Few important Governor Limits in Salesforce
In one transaction, we can use a maximum of 100 SOQL queries.
In one transaction, we can use a maximum of 20 SOSL queries.
In one transaction, we can use a maximum of 150 DML statements.
In one transaction, we can fetch a maximum of 50k records in SOQL.
In one transaction, we can fetch a maximum of 2k records in SOSL.
But you can use Nested "For" Loops since it decreases performance. To avoid nested loop then you used Map
public class MapEx {
public static void createMap(){
try{
List<Account> accountList = [select id from Account ];
set<Id> accIds =new set<Id>();
for(Account acc:accountList){
accIds.add(acc.Id);
}
System.debug('accIds-> '+accIds);
List<Contact> contactList = new List <Contact>();
contactList = [select id,AccountId from Contact where AccountID IN : accIds ];
Map<Id,long> accId_contactMap = new Map<Id,long>();
for(Contact con:contactList){ // accouuntId - nuber of related contact
if(accId_contactMap.ContainsKey(con.AccountId)){
long count = accId_contactMap.get(con.AccountId);
accId_contactMap.put(con.AccountId , count+1);
}
else{
accId_contactMap.put(con.AccountId , 1);
}
}
System.debug('accId_contactMap-->'+accId_contactMap);
}catch(Exception e){
System.debug('get exception on line-->'+e.getLineNumber()+' error is-->'+e.getMessage());
}
}
}
I hope you find the above solution helpful. If it does, please mark as Best Answer to help others too.
Thanks and Regards,
Deepali Kulshrestha
www.kdeepali.com