Join comparison

This is a slight modification of the standard DAX Development III example of joins being used to increase performance. I expect the data set I've chose isn't ideal to highlight the concept, but it's adequate for my purpose, which is to demonstrate that the concept holds:

static void Nathan_Join(Args _args)
{
    System.DateTime first, second;
    System.TimeSpan ts;
    str dummy;
    LedgerTrans lTr;
    LedgerTable lTa;
    AmountMST amount;
    str message;
    ;

    flush LedgerTable;
    flush LedgerTrans;
    first = System.DateTime::get_Now();
    while select AccountNum from lTa where lTa.AccountName like 'Bank*'
    {
        while select lTr
            where lTr.accountNum == lTa.accountNum
        {
            amount += lTr.amountMST;
        }
    }
    second = System.DateTime::get_Now();
    ts = second.Subtract(first);
    message += ts.ToString();
    message += strFmt("\nNo join: %1\n", amount);

    amount = 0;
    flush LedgerTable;
    flush LedgerTrans;
    first = System.DateTime::get_Now();
    while select accountNum from lTa where lTa.AccountName like 'Bank*'
        join amountMST from lTr
        where lTr.accountNum == lTa.accountNum
    {
        amount += lTr.amountMST;
    }
    second = System.DateTime::get_Now();
    ts = second.Subtract(first);
    message += ts.ToString();
    message += strFmt("\nJoin amount: %1", amount);

    info(message);
}

Result:
00:00:02.5510000
No join: 36,289,571.52
00:00:02.1480000
Join amount: 36,289,571.52

Less that 100% of difference. Smaller scale of difference than the field list and aggregation testing. As mentioned, different data sets would produce different results. If performance matters, it's always worth profiling alternatives - and checking the result is consistent between all alternatives :-)

Note, I've rejigged the output approach so a single infolog message it produced. This is easier to copy/paste into here!