将数据存储区实体链接到其Blobstore映像的最佳方法？ [英] Best way to link datastore entity to its blobstore image?

问题描述

  class contact（db.Model）：
 email = db.EmailProperty（）
 image = #Hmm。 
  

我的联系人图片将存储在Blobstore中，并以各种尺寸显示。

因此，我应该使用 db.ReferenceProperty（BlobInfo），以便我可以通过执行以下操作：

  get_serving_url（alice.image.key，size = x）
  

或者我应该使用 db.StringProperty ，以便我不必为了获得密钥而进行第二次读取：

  get_serving_url（alice.image，size = x）
  

或者我应该使用基本URL的 db.LinkProperty ，后期修正所需的大小：

  alice.image +'= sx'
  

---

我不预见需要除键之外的任何东西，所以我认为第二个比第一个好。

虽然我不确定第三个是不是最好的，因为我不确定它是否与创建唯一URL一样高效，它可以缓存，以避免重复生成相同的缩略图 - 或者这两种情况下自动处理？

解决方案

经过一些实验，我想我可以回答我自己的问题。

好的，有点。事实证明，答案是这不是一个真正的问题开始。

虽然 get_serving_url（）给人的印象是正在做某事，实际上'服务URL'只不过是提供的 BlobKey 的后期修改。

更重要的是，提供 size = x 只会追加 = sx - 没有什么特别的，或多或少有效，就这样做。最后， __ BlobInfo __ 实体种类使用 BlobKey 作为它的关键名称，所以它也很容易从另一个访问。

---

我决定使用，并建议任何人都有同样的困境，我的第三个选择：

  imgBlob = db。 LinkProperty（）
  

很容易：

附加任何调整大小/裁剪要求

给出默认值/ make不需要重载 put（）

Let's say I have a model for my email address book:

class contact(db.Model):
    email = db.EmailProperty()
    image = #Hmm.

My contacts' images will be stored in the Blobstore, and served at various sizes.

So, should I use a db.ReferenceProperty(BlobInfo) such that I can serve it by doing:

get_serving_url(alice.image.key, size=x)

Or should I use a db.StringProperty so that I don't have to make the second read in order to get the key:

get_serving_url(alice.image, size=x)

Or should I use a db.LinkProperty for the base URL, post-fixing the size needed:

alice.image+'=sx'

---

I don't foresee needing anything other than the key, so I think the second is better than the first.

Though I am unsure if the third is best because I am unsure whether it is as efficient as creating a unique URL, which can be cached to avoid repeatedly generating the same thumbnail - or is this handled automagically in both cases?

解决方案

After some experimentation, I think I can answer my own question.

Well, sort of. It turns out that the answer is "this wasn't a real problem to begin with".

While get_serving_url() gives the impression that something fancy is being done, actually the 'serving URL' is nothing more than a post-fixing of the supplied BlobKey.

What's more, supplying size=x merely appends =sx - there's nothing special, more or less efficient, about doing it this way. My second and third options, really are identical.

Finally, the __BlobInfo__ entity kind uses the BlobKey as its key name, so it is also easy to access from the other.

---

I have decided to use, and would suggest to anyone with the same dilemma, my third option:

imgBlob = db.LinkProperty()

It is then easy to:

• append any resizing/cropping requirements
• give a default value/make required without overloading put()

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