Till now, we have examined the internals of datastore, how it is built on top of BigTable, and how we can model our data around it. This, of course, makes us store whatever we want to, but it is useless until we can retrieve what was stored. Datastore provides us with a way to query the stored data with two parallel interfaces. One is an API, which is used to query data, and another is an SQL-like language called Google Query Language (GQL).
In this chapter, we will learn the following:
Querying your data
The way queries work and the limitations of what can be queried
The query API and GQL
Transactions
So, that's a tall order. Let's start our journey.