Filter entities on a sub-entity property in Google Datastore query

Question

My Datastore entities are going to have properties of embedded entity type.

After I save them as following (I'm using gcloud v0.27.0):

dataset.save([{
    key: dataset.key({ path: ['MyKind', 1] }),
        data: {
            foo: 'bar',
            zxc: {
                nested: {
                    foobar: 32
                }
            }
        }
    }, 
    {
        key: dataset.key({ path: ['MyKind', 2] }),
        data: {
            foo: 'a string',
            zxc: {
                nested: {
                    foobar: 132
                }
            }
        }
    }
    ], function(error) { console.log(error); });

Is there any way to query entities that, say, have zxc.nested.foobar=132?

I run query like on the picture below and it shows no result.

Answer 1

You can do this by joining the property names with dots and using that joined string as the property name in the query.

In the Cloud Datastore v1beta3 API, the JSON request would look like:

{
  "query": 
  {
    "kinds": 
    [
      {
        "name": "MyKind"
      }
    ],
    "filter": 
    {
      "propertyFilter": 
      {
        "property": 
        {
          "name": "zxc.nested.foobar"
        },
        "operator": "EQUAL",
        "value": 
        {
          "integerValue": "132"
        }
      }
    }
  }
}

Note in order for a result to appear, each of the properties must be indexed. This is the case by default in the JSON API:

{
  "key": 
  {
    "path": 
    [
      {
        "kind": "MyKind",
        "id": 1
      }
    ]
  },
  "properties": 
  {
    "zxy": 
    {
      "entityValue": 
      {
        "properties": 
        {
          "nested": 
          {
            "entityValue": 
            {
              "properties": 
              {
                "foobar": 
                {
                  "integerValue": "132"
                }
              }
            }
          }
        }
      }
    }
  }
}

Datastore client libraries typically also index properties by default, but some older versions of gcloud-node (e.g. 0.27.0) may not.