Property filter query

Use a property filter query.

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For detailed documentation that includes this code sample, see the following:

Code sample

C#

To learn how to install and use the client library for Datastore mode, see Datastore mode client libraries. For more information, see the Datastore mode C# API reference documentation.

To authenticate to Datastore mode, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

Key key = _db.CreateKeyFactory("__kind__").CreateKey("Task");
Key startKey = new KeyFactory(key, "__property__")
    .CreateKey("priority");
Query query = new Query("__property__")
{
    Filter = Filter.GreaterThanOrEqual("__key__", startKey)
};
var properties = new List<string>();
foreach (Entity entity in _db.RunQuery(query).Entities)
{
    string kind = entity.Key.Path[0].Name;
    string property = entity.Key.Path[1].Name;
    properties.Add($"{kind}.{property}");
};

Java

To learn how to install and use the client library for Datastore mode, see Datastore mode client libraries. For more information, see the Datastore mode Java API reference documentation.

To authenticate to Datastore mode, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

Key startKey =
    datastore
        .newKeyFactory()
        .setKind("__property__")
        .addAncestors(PathElement.of("__kind__", "Task"))
        .newKey("priority");
Query<Key> query =
    Query.newKeyQueryBuilder()
        .setKind("__property__")
        .setFilter(PropertyFilter.ge("__key__", startKey))
        .build();
Map<String, Collection<String>> propertiesByKind = new HashMap<>();
QueryResults<Key> keys = datastore.run(query);
while (keys.hasNext()) {
  Key key = keys.next();
  String kind = key.getParent().getName();
  String propertyName = key.getName();
  Collection<String> properties = propertiesByKind.get(kind);
  if (properties == null) {
    properties = new HashSet<String>();
    propertiesByKind.put(kind, properties);
  }
  properties.add(propertyName);
}

PHP

To learn how to install and use the client library for Datastore mode, see Datastore mode client libraries. For more information, see the Datastore mode PHP API reference documentation.

To authenticate to Datastore mode, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

$ancestorKey = $datastore->key('__kind__', 'Task');
$startKey = $datastore->key('__property__', 'priority')
    ->ancestorKey($ancestorKey);
$query = $datastore->query()
    ->kind('__property__')
    ->filter('__key__', '>=', $startKey);
$result = $datastore->runQuery($query);
/* @var array<string> $properties */
$properties = [];
/* @var Entity $entity */
foreach ($result as $entity) {
    $kind = $entity->key()->path()[0]['name'];
    $propertyName = $entity->key()->path()[1]['name'];
    $properties[] = "$kind.$propertyName";
}

Ruby

To learn how to install and use the client library for Datastore mode, see Datastore mode client libraries. For more information, see the Datastore mode Ruby API reference documentation.

To authenticate to Datastore mode, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

start_key = datastore.key [["__kind__", "Task"], ["__property__", "priority"]]
query = datastore.query("__property__")
                 .select("__key__")
                 .where("__key__", ">=", start_key)

entities = datastore.run query
properties_by_kind = entities.each_with_object({}) do |entity, memo|
  kind = entity.key.parent.name
  prop = entity.key.name
  memo[kind] ||= []
  memo[kind] << prop
end

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