CODEWITHSUNDEEP
google-app-enginegoogle-cloud-datastoreobjectify
learner
learner

Reputation: 11780

Use Objectify to get projection of entity by Id

I have the id of an entity from which I only need a single field. Is there a way to get that projection or must I fetch the whole entity? Here is the code that I thought should do it.

bookKey =OfyService.ofy().load().type(Page.class).id(pageId).project("bookKey").now();

Upvotes: 0

Views: 185

Answers (1)

stickfigure
stickfigure

Reputation: 13556

The datastore is a key-value store which loads objects whole, not field-by-field. This is quite different from how you work with a relational database.

There is an exception to this which allows you to load data directly out of an index (projection queries), however it is a performance optimization with very limited and specific use. In general, if you don't understand the fairly exotic detail of how projections work, you should not be using them - it's a premature optimization.

Upvotes: 1

Related Questions