[FIX] account, sale: create invoice lines in batch

This patch changes the create of `account.invoice.line` to use
`model_create_multi`, which allows the batch creation of multiple
invoice lines while only triggering the recompute of all related fields
once.

It also changes the generation of invoices from a SO to take advantage
of the create multi of `account.invoice.line`.

For a SO of 2000 lines:
    Pre-patch:
        ~417s to generate an Invoice
    Post-patch:
        ~30s to generate an Invoice

closes odoo/odoo#31975

Signed-off-by: Raphael Collet (rco) <rco@openerp.com>

addons/account/models/account_invoice.py

@@ -1865,12 +1865,12 @@ class AccountInvoiceLine(models.Model):
         }
         return data
 
-    @api.model
-    def create(self, vals):
-        if vals.get('display_type', self.default_get(['display_type'])['display_type']):
-            vals.update(price_unit=0, account_id=False, quantity=0)
-
-        return super(AccountInvoiceLine, self).create(vals)
+    @api.model_create_multi
+    def create(self, vals_list):
+        for vals in vals_list:
+            if vals.get('display_type', self.default_get(['display_type'])['display_type']):
+                vals.update(price_unit=0, account_id=False, quantity=0)
+        return super(AccountInvoiceLine, self).create(vals_list)
 
     @api.multi
     def write(self, values):

addons/sale/models/sale.py

@@ -522,6 +522,8 @@ class SaleOrder(models.Model):
             # We only want to create sections that have at least one invoiceable line
             pending_section = None
 
+            # Create lines in batch to avoid performance problems
+            line_vals_list = []
             for line in order.order_line:
                 if line.display_type == 'line_section':
                     pending_section = line
@@ -543,14 +545,21 @@ class SaleOrder(models.Model):
 
                 if line.qty_to_invoice > 0 or (line.qty_to_invoice < 0 and final):
                     if pending_section:
-                        pending_section.invoice_line_create(invoices[group_key].id, pending_section.qty_to_invoice)
+                        line_vals_list.extend(pending_section.invoice_line_create_vals(
+                            invoices[group_key].id,
+                            pending_section.qty_to_invoice
+                        ))
                         pending_section = None
-                    line.invoice_line_create(invoices[group_key].id, line.qty_to_invoice)
+                    line_vals_list.extend(line.invoice_line_create_vals(
+                        invoices[group_key].id, line.qty_to_invoice
+                    ))
 
             if references.get(invoices.get(group_key)):
                 if order not in references[invoices[group_key]]:
                     references[invoices[group_key]] |= order
 
+            self.env['account.invoice.line'].create(line_vals_list)
+
         for group_key in invoices:
             invoices[group_key].write({'name': ', '.join(invoices_name[group_key]),
                                        'origin': ', '.join(invoices_origin[group_key])})
@@ -1363,18 +1372,34 @@ class SaleOrderLine(models.Model):
     @api.multi
     def invoice_line_create(self, invoice_id, qty):
         """ Create an invoice line. The quantity to invoice can be positive (invoice) or negative (refund).
+
+            .. deprecated:: 12.0
+                Replaced by :func:`invoice_line_create_vals` which can be used for creating
+                `account.invoice.line` records in batch
+
             :param invoice_id: integer
             :param qty: float quantity to invoice
             :returns recordset of account.invoice.line created
         """
-        invoice_lines = self.env['account.invoice.line']
+        return self.env['account.invoice.line'].create(
+            self.invoice_line_create_vals(invoice_id, qty))
+
+    def invoice_line_create_vals(self, invoice_id, qty):
+        """ Create an invoice line. The quantity to invoice can be positive (invoice) or negative
+            (refund).
+
+            :param invoice_id: integer
+            :param qty: float quantity to invoice
+            :returns list of dict containing creation values for account.invoice.line records
+        """
+        vals_list = []
         precision = self.env['decimal.precision'].precision_get('Product Unit of Measure')
         for line in self:
             if not float_is_zero(qty, precision_digits=precision) or not line.product_id:
                 vals = line._prepare_invoice_line(qty=qty)
                 vals.update({'invoice_id': invoice_id, 'sale_line_ids': [(6, 0, [line.id])]})
-                invoice_lines |= self.env['account.invoice.line'].create(vals)
-        return invoice_lines
+                vals_list.append(vals)
+        return vals_list
 
     @api.multi
     def _prepare_procurement_values(self, group_id=False):