A data object in the App Engine datastore is known as an entity. An entity has one or more properties, named values of one of several data types, including integers, floating point values, strings, dates, binary data, and more.
Each entity also has a key that uniquely identifies the entity. The simplest key has a kind and a unique numeric ID provided by the datastore. The ID can also be a string provided by the application.
An application can fetch an entity from the datastore by using its key, or by performing a query that matches the entity's properties. A query can return zero or more entities, and can return the results sorted by property values. A query can also limit the number of results returned by the datastore to conserve memory and run time.
Unlike relational databases, the App Engine datastore does not require that all entities of a given kind have the same properties. The application can specify and enforce its data model using Slim3.
A property can have one or more values. A property with multiple values can have values of mixed types. A query on a property with multiple values tests whether any of the values meets the query criteria.
Continue to Queries and Indexes.