If I understand you correctly.

1. CRUD, is write(), not update(), odoo ORM naming the way it is.

2. write() can update multiple records and its corresponding fields at the same time.

3. update() is designed to work with pseudo-records.

The only benefit of write() is the ability to update multiple records. Otherwise use update() in custom function?

I make this conclusion because update() can update existed records as well. I've not tried update() multiple yet though.

When setting multiple fields at the same time use write() so that if it takes a number of field values the function writes them to all the records in its recordset. self.write({'name':'Name', 'age': age})

So gives you single update statement in the database.

But update() only works on singletons and performs a database write for each written field.So at a time it updates only single record.It Iterates through the fields and sets each one separately giving you multiple update statements in the database.

for order in self:

amount_untaxed = amount_tax = 0.0

for line in order.order_line:

amount_untaxed += line.price_subtotal

amount_tax += line.price_tax

order.update({

'amount_untaxed': amount_untaxed,

'amount_tax': amount_tax,

'amount_total': amount_untaxed + amount_tax,

})

and it can be used within onchange functions as they return pseudo records.ie.update function can work on records not present in database yet.

Thank you very much for the clears up.

I was doing it wrong by abusing for-loop with update().