Yii2 handling non normalized columns

Question to all Yii2 normalization geeks out there.

Where is the best place to set non-normalized columns in Yii2?

Example, I have models Customer, Branch, CashRegister, and Transaction. In a perfect world, and in a perfectly normalized Database, our Transaction model would have only the cashregister_id, The CashRegister would store branch_id, and the Branch would store customer_id. However due to performance issues, we find ourselves obliged sometimes though to have a non-normalized Transaction model containing the following:

1. cashregister_id
2. branch_id
3. customer_id

When creating a transaction, I want to store all 3 values. Setting

$transaction->branch_id = $transaction->cashRegister->cashregister_id;
$transaction->customer_id = $transaction->cashRegister->branch->customer_id;

however in the controller does not feel correct.

One solution would be to do this in aftersave() in the Transaction model and make those columns read-only. But this also seems better but not perfect.

I wanted to know what is the best practice or where is the best place to set those duplicate columns, to make sure that the data integrity is maintained?

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