Batchjob: number of record receivable by a subquery - subquery

Question

I'm relatively new to Apex, but I have some questions about a batch job that I am creating. I want to make a query with a subquery (please see the code). Every Portal_c can have more than 200 Exporte_r.
global Database.QueryLocator start(Database.BatchableContext BC) {
String query = 'SELECT Id, Name, (SELECT Id FROM Exporte__r) FROM Portal__c';
return Database.getQueryLocator(query);
}
global void execute(Database.BatchableContext BC, List<Portal__c> scope) {
for (Portal__c portal : scope) {
// doesn't work -> First error: Aggregate query has too many rows for direct assignment, use FOR loop
// when using FOR loop -> System.QueryException: invalid query locator
//List<Export__c> relatedExports = portal.Exporte__r;
// grab all the related Export__c records using 'getSObjects' to avoid errors described above
Export__c[] relatedExports = portal.getSObjects('Exporte__r');
if (relatedExports != null) {
for (Export__c exp : relatedExports) {
// do something
}
}
}
}
I have the following questions:
If I use List<Export__c> relatedExports = portal.Exporte__r (which I commented out) to get the sub query records then I will receive the error message: “Aggregate query has too many rows for direct assignment, use FOR loop”. The error message makes no sense for me as the SOQL is done already before. Is there any explaination?
With the solution above the maximal amount of records from type Exporte_r received per Portal_c with the sub query is 199 though I have more than 200 for some records of Portal__c, why is it limited to that number? It seems all records above 199 are ignored in this case.
Is there any possibility to receive more than 199 records from a sub query? I have tried to change the batch size but it seems it is independent of the number of records receivable by the sub query. Any idea?
Many thanks!

Answer 1

As per the salesforce doc http://www.salesforce.com/us/developer/docs/apexcode/Content/langCon_apex_loops_for_SOQL.htm
You might get a QueryException in a SOQLfor loop with the message
Aggregate query has too many rows for direct assignment, use FOR loop.
This exception is sometimes thrown when accessing a large set of child
records of a retrieved sObject inside the loop, or when getting the
size of such a record set. To avoid getting this exception, use a for
loop to iterate over the child records, as follows.
Integer count=0;
for (Contact c : returnedAccount.Contacts) {
count++;
// Do some other processing
}