CODEWITHSUNDEEP
google-app-enginegoogle-cloud-datastore
user2924127
user2924127

Reputation: 6240

Key vs ID/Name?

I do not want to create an autogenerated key for my entities so I specify my own:

Entity employee = Entity.newBuilder().setKey(makeKey("Employee", "bobby"))
        .addProperty(makeProperty("fname", makeValue("fname").setIndexed(false)))
        .addProperty(makeProperty("lname", makeValue("lname").setIndexed(false)))    
        .build();

CommitRequest request = CommitRequest.newBuilder()
    .setMode(CommitRequest.Mode.NON_TRANSACTIONAL)
    .setMutation(Mutation.newBuilder().addInsert(employee))
    .build();
datastore.commit(request);

When I check to see what the entity looks like it looks like this:

enter image description here

Why is this auto-generated key generated if I specified my own key (bobby)? It seems bobby was also created, but now I have bobby and this autogenerated key. What is the difference between the key and id/name?

Upvotes: 1

Views: 2900

Answers (3)

Dan Cornilescu
Dan Cornilescu

Reputation: 39824

You can't specify your own key, keys actually contain information necessary for the datastore operation. This note in the documentation gives you an idea:

Note: The URL-safe string looks cryptic, but it is not encrypted! It can easily be decoded to recover the original entity's kind and identifier:

key = Key(urlsafe=url_string)
kind_string = key.kind()
ident = key.id()

If you use such URL-safe keys, don't use sensitive data such as email addresses as entity identifiers. (A possible solution would be to use the MD5 hash of the sensitive data as the identifier. This stops third parties, who can see the encrypted keys, from using them to harvest email addresses, though it doesn't stop them from independently generating their own hash of a known email address and using it to check whether that address is present in the Datastore.)

What you can specify is the ID portion of the key, either as a number or as a string:

A key is a series of kind-ID pairs. You want to make sure each entity has a key that is unique within its application and namespace. An application can create an entity without specifying an ID; the Datastore automatically generates a numeric ID. If an application picks some IDs "by hand" and they're numeric and the application lets the Datastore generate some IDs automatically, the Datastore might choose some IDs that the application already used. To avoid, this, the application should "reserve" the range of numbers it will use to choose IDs (or use string IDs to avoid this issue entirely).

Upvotes: 5

Daniel Roseman
Daniel Roseman

Reputation: 599610

This is the url-safe version of your key, suitable for use in links. Use KeyFactory.stringToKey to convert it to an actual key, and you'll see that it contains your string name.

Upvotes: 3

konqi
konqi

Reputation: 5227

What you create with makeKey("Employee", "bobby") is a key for an Entity with the entity name Employee and the name bobby. What you see as Key in the datastore viewer is a representation for exactly that.

Generally speaking a key always consists of

  • optional parent key (with entity type and name/id)
  • entity type
  • entity name/id

Maybe someone here can tell you how to decode the key into its components but rest asured that you're doing everything right and the behavior is as expected.

Upvotes: 1

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