Hello all,

I have created a new postgresql view which has the same code than account.invoice.report (totally duplicated). We took the code on Odoo 8. So this report is in the old api.

I want to create a new column in the graph associated to this view : invoice week. Invoice_week is the week in the year of the date_invoice for each invoice.

<record id="view_account_invoice_report_graph_vtm2" model="ir.ui.view">
         <field name="name">account.invoice.report.graph.vtm2</field>
         <field name="model">account.invoice.report.vtm2</field>
         <field name="arch" type="xml">
             <graph string="Invoices Analysis" type="pivot">
                 <field name="fiscal_position" type="row"/>
                 <field name="invoice_week" type="col"/>
                 <field name="price_total" type="measure"/>
                 <field name="nbr" type="measure"/>
             </graph>
         </field>
    </record>

So, I have created a new computed field on the report model. I wanted the invoice_week computed on the fly when the report is generated. My function _finddate is ok and can extract the week of an invoice according to his date_invoice :

'invoice_week' : fields.function(_finddate, string="Semaine de la facture", type='char', readonly=True),

But I get this error :

AssertionError: Fields in 'groupby' must be regular database-persisted fields (no function or
 related fields), or function fields with store=True

My question is : do I have to imperatively create a new stored field on the account.invoice model or it is possible to calculate the invoice_week on the fly according to the date_invoice?

Or : Do postgresql views really work only with stored field somewhere in the database?

EDIT #1

If I add a new field 'invoice_week' on account.invoice model, it would be computed like this. So it would be the week of the year calculated with the date_invoice :

from openerp import models, fields, api, _

from datetime import datetime
class account_invoice(models.Model):
    _inherit = "account.invoice"
    invoice_week = fields.Char(compute='_findweek',string="Semaine de la facture", readonly=True, store=True)
        
    @api.one
    @api.depends('date_invoice')
    def _findweek(self):
        for invoice in self:
            if invoice.date_invoice:
                invoice.invoice_week = datetime.strptime(invoice.date_invoice, "%Y-%m-%d").strftime('%U')