No Results from Multi-property Projection Query in Google Cloud Datastore
<p>I'm trying to query the database with:  </p>

<pre><code>fields = "property_1, property_2, ... property_n"  
query = "SELECT {0} FROM Table WHERE property_{n+1} = '{1}'".format(fields, property_{n+1})  
all_objs = CacheDatastore.fetch(query, refresh=True)  
</code></pre>

<p>The problem is that the returned list is empty, while if the query is like </p>

<p><code>"SELECT * FROM Table WHERE property_{n+1} ='{1}'"</code>, I receive the full set.
I've created the necessary indexes and have deployed them, so it is not from there.  </p>

<p>The log says that a Blob key is not found, but none of the properties is different from <code>string</code>, <code>float</code> or <code>int</code>...</p>

<p>It turned to be a bug in the db library which is no longer in development, so I'm leaving here the link to the ticket and the comments on it.<br>
  GAE allows indexing of static members of the db.Model class hierarchy, but returns 0 results for projection queries where the static member is included
among the projected properties.
<a href="https://code.google.com/p/google-cloud-platform/issues/detail?id=119" rel="nofollow">https://code.google.com/p/google-cloud-platform/issues/detail?id=119</a></p>

python google-app-engine cloud google-cloud-datastore projection