On Tuesday, 20 August 2013 10:57:52 UTC+1, Victor Hooi wrote:
> Hi,
>
> *1. Bulk Creating Products/ProductImages*
>
> I have a Django custom management command that bulk-loads a list of
> products and product images from a JSON file.
>
> I have a Product model, along with an ProductImage model - each Product
> may have many ProductImages.
>
> class Product(models.Model):
>> ...
>> name = models.CharField(max_length=200, help_text='Name of this
>> product.')
>> description = models.TextField(help_text='Short description of this
>> product.')
>> external_id = models.CharField(max_length=100, unique=True,
>> help_text='Unique identifier for this product provided by the supplier.')
>> brand = models.ForeignKey(Brand)
>> supplier = models.ForeignKey(Supplier)
>> selling_price = models.DecimalField(max_digits=10, decimal_places=2,
>> help_text='The price which we\'re selling this product at.')
>> original_price = models.DecimalField(max_digits=10, decimal_places=2,
>> help_text='The original retail price of this product, before any
>> discounts.')
>> current_stock_level = models.PositiveIntegerField(default=0)
>> current_sold_count = models.PositiveIntegerField(default=0)
>> ...
>
>
> class ProductImage(models.Model):
>> product = models.ForeignKey(Product, related_name='images')
>> image = models.ImageField(max_length=200, upload_to='product_images')
>> # TODO - Do we actually want to make retina images a distinct column
>> in the database? May need to revisit this.
>> retina_image = models.ImageField(max_length=200,
>> upload_to='product_images')
>> size = models.ForeignKey(ImageSize)
>> ordinal = models.PositiveIntegerField(default=0)
>> class Meta:
>> ordering = ['ordinal']
>> unique_together = ('product', 'size', 'ordinal')
>> def __unicode__(self):
>> return u'%s image %i for %s' % (self.size, self.ordinal,
>> self.product.name)
>
>
> I have a single look that iterates through the JSON file, creating a list
> of Products, as well as a list of ProductImages that link back to those
> products. (The below is an extract)
>
> products = []
>> product_images = []
>> ...
>> for product in json_data:
>> brand, created_new_brand =
>> Brand.objects.get_or_create(name=product['brand'])
>> if created_new_brand:
>> new_brands_created += 1
>> ...
>> current_product = Product(name = product['name'],
>> brand = brand,
>> supplier = supplier,
>> description =
>> product['description'],
>> ...
>> )
>> ...
>> for image_set in product['images']:
>> for size in image_sizes.keys():
>> product_images.append(ProductImage(product =
>> current_product,
>> image =
>> image_set[size],
>> retina_image =
>> image_set[size],
>> size =
>> image_sizes[size],
>> ordinal =
>> image_set_counter,
>> ))
>> image_set_counter += 1
>> ...
>> Product.objects.bulk_create(products)
>> ...
>> for product_image in product_images:
>> product_image.save()
>
>
> I then call bulk_create() on the products list, which succeeds.
>
> However, when I try to call .save() or bulk_create() on the ProductImage,
> they fail, saying that product_id is NULL.
>
> IntegrityError: null value in column "product_id" violates not-null
>> constraint
>> DETAIL: Failing row contains (8, null,
>> https://cdn.foobar.com.au/site_media/uploads/product_im...,
>> https://cdn.foobar.com.au/site_media/uploads/product_im..., 4, 0).
>
>
> If I actually inspect one one of the items in the ProductImages list -
> product_image.product seems to point to a valid product, however,
> product_image.product_id seems to be None:
>
> ipdb> p product_image.product
>> <Product: Widget 101 #4383>
>> ipdb> p product_image.product_id
>> None
>
>
> This is strange, because if I manually create the same ProductImage from
> the shell, the product_image.product_id field is populated.
>
> I'm guessing this product_id field should resolve to the pk id of the
> product in product_image.product, right?
>
> However, in my case, when I instantiate each ProductImage and set it to a
> Product, that actual Product hasn't been saved to the database - I'm
> guessing that Product.id hasn't been generated yet, and the ProductImage
> object I have is somehow broken?
>
> Is there another way I can achieve this then? (Loop through file, creating
> a list of Products and ProductImages, then bulk_creating them?)
>
> *2. Image Set Counter*
>
> Also, second question - in the last code segment above, I have a
> image_set_counter that I use to set the ordinal - basically,
> product['images'] is actually a list of several images. I'm using the
> counter to set the ordinal. However, am I better off doing some kind of:
>
> for image_set_counter in xrange(len(product['images'])):
>> ...
>
> product['images'][image_set_counter]
>
>
> and using product['images'][image_set_counter] to access it?
>
> Cheers,
> Victor
>
1. You need to save the Product before it can be added to the ProductImage.
2. Neither. You should use `enumerate()` to give you an index:
for counter, image_set in enumerate(product['images']):
--
DR.
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