Hi all, Would appreciate some help on how to optimise the following piece of code.
I have two models, "invoice" and "invoice item". The invoice total is calculated in invoice_total() by aggregation the sub_total and tax_total from all invoice_items (see code below). The problem I have is that even though I prefetch all the invoice_items in the view, when invoice.invoice_total is called in a template 3 identical queries will be run for each invoice. For example see some output from a profile. # All invoice items are prefetched correctly SELECT ••• FROM `billing_invoice_item` WHERE `billing_invoice_item`.`invoice_id` IN (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 51, 53, 54, 55, 56, 58, 59, 60, 61, 62, 65, 66, 67, 68, 69, 70, 72, 73, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 87, 88, 89, 90, 91, 92, 93, 94, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 128, 129, 130, 131, 132, 134, 135, 136, 137, 138, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277) but then after this the table is queried 3 more times SELECT ••• FROM `billing_invoice_item` WHERE `billing_invoice_item`.`invoice_id` = 277 SELECT ••• FROM `billing_invoice_item` WHERE `billing_invoice_item`.`invoice_id` = 277 SELECT ••• FROM `billing_invoice_item` WHERE `billing_invoice_item`.`invoice_id` = 277 I'm using django 1.5 and my code is below. Any thoughts? #models.py class Invoice(models.Model): customer = models.ForeignKey(Customer) : : : def invoice_total(self): invoice_total = self.invoice_item_set.aggregate(Sum('sub_total'), Sum('tax_total')) return str(round(invoice_total['sub_total__sum'], 2)) class Invoice_Item(models.Model): invoice = models.ForeignKey('Invoice') sub_total = models.DecimalField(blank=True, null=True, max_digits=9, decimal_places=2) tax_total = models.DecimalField(blank=True, null=True, max_digits=9, decimal_places=2) : : : #views.py def invoice(request): invoices = Invoice.objects.all().prefetch_related('invoice_item_set', 'journals', 'journals__transaction_set', 'journals__transaction_set__account', 'customer') return render_to_response('billing/invoices.html', {'invoices': invoices,}, context_instance=RequestContext(request)) -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscr...@googlegroups.com. To post to this group, send email to django-users@googlegroups.com. Visit this group at http://groups.google.com/group/django-users. For more options, visit https://groups.google.com/groups/opt_out.