Question

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How to model many blobs for an object?

I have a datastore model called Location and I would like users to be able to upload a multitude of images relating to that location. I know that I can reference those images from the Blobstore using the BlobReferenceProperty but how can I reference a lot of these properties without creating many more attributes?

Can I create a list of them or make a list property of BlobReferenceProperties?

Answer 1

As with any basic datastore supported type, you can use a ListProperty of BlobKey.

blobRefs = db.ListProperty(blobstore.BlobKey)

Please note:

1. List properties retain order. This is quite useful in some situations.
2. Whole list gets serialized and stored inside the entity. There is no way to just get a part of it.
3. If property is indexed, then every entity will get it’s own entry in index (or two if you index for ascending and descending). There can be a max of 5000 index entries per entity.
4. It you create a compound index with two list properties in this will lead to exploding indexes.