立即查询已保存的实体有时会返回null-数据存储区

Question

I am saving an entity kind 'review' with following properties

review {
  _id : 4e0590ae-7603-44ff-8333-b3d06546914f
  text : 'Nice review'
}

I am saving it with a AJAX call and on success response I am passing _id and querying for saved review in another AJAX call. Sometimes I am getting null which results in NullPointerException. In datastore storing entity takes more time? If takes then the first AJAX call should not return till put operation completes. Is there any configuration I am missing?

Answer 1

In datastore, you don't have instantaneous strong consistency. You have eventual consistency while your data replicates and your indices get populated.

To force consistency, you need either ancestor queries , or get-by-key queries .

Look up this article for more ideas on how to structure your data.