Objectify queries are very slow (Google Datastore)

Question

After some refactoring, we are having issues with the objectify queries that we are using in the application. The strange thing is that even if we revert to the original code the problem stays.

When the application starts, a number of 250 books are fetched from the Datastore using Objectify. The caching is enabled and seems to be working. The problem is that it takes around 50 - 60 seconds to get the result, and for this reason sometimes the http request is killed. We never had this issues before and we can't find an answer to it. If I ran a query like "select * from BookEntity order by creationDate desc limit 250" in the Google Datastore console and it took 5 - 7 seconds not more.

Before the refactoring, the book entity looked something like this:

@Index
@Entity
@Cache
public class BookEntity {
    @Index
    public String title_name;
    @Index
    public String author_name;
    public String isbn;
    public int number_of_pages;
    public Ref<PdfEntity> book_pdf;
}

Now it's like this:

@Index
@Entity
@Cache
public class BookEntity {
    @Index
    @AlsoLoad("title_name")
    private String titleName;

    @Index
    @AlsoLoad("author_name")
    private String authorName;

    private String isbn;

    @AlsoLoad("number_of_pages")
    private int numberOfPages;

    @AlsoLoad("book_pdf")
    private Ref<PdfEntity> bookPdf;

    // getters and setters for the fields because now they are private
}

Here is just an example, but in reality it has around 20 fields. In order to migrate the schema to the field names, I ran a task in GAE which loaded and then saved again all the BookEntity entities.

This example can be extended to all the entities that are used in the application, but the book is the worst performing one. Even though nothing is changed in the query, and we are talking about a basic query which fetches the newest 250 books by creationDate, it takes a lifetime to get the actual result. Any idea how I can investigate this issues further?

Cristian Cristian · Accepted Answer · 2016-11-07T14:46:54

Problem found. We were persisting some information in the non-args constructor of the BookEntity, so for every book fetched from the datastore 3 save operations were made for some other entities which are referred from the book.

Objectify queries are very slow (Google Datastore)

1 Answers