[IMP] update readme

onchange_helper/README.rst

@@ -30,9 +30,11 @@ You can also use it on existing record for example:
 
     `vals = sale.play_onchanges(vals, ['partner_shipping_id'])`
 
-Then the onchange will be played with the vals passed and the existing vals of the sale. `vals` will be updated with partner_invoice_id, pricelist_id, etc...
+Then the onchange will be played with the vals passed and the existing vals of the sale. `vals` will be updated with partner_invoice_id, pricelist_id, etc..
 
 
+Behind the scene, `play_onchanges` will execute **all the methods** registered for the list of changed fields, so you do not have to call manually each onchange. To avoid performance issue when the method is called on a record, the record will be transformed into a memory record before calling the registered methods to avoid to trigger SQL updates command when values are assigned to the record by the onchange
+
 Bug Tracker
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