google-cloud-datastore

问题 I am using Google Cloud's Datastore Client Library for Java to access the Cloud Datastore. Note : I am not using App Engine to deploy my application; just running a local application for development purposes. Following the example, I can read/write to the Cloud Datastore. Datastore datastore = DatastoreOptions.defaultInstance().service(); KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind"); Key key = keyFactory.newKey(); Entity entity = datastore.get(key); I want to be able to

问题 Google flexible app engine spring boot project running on local with datastore is giving the com.google.cloud.datastore.DatastoreException Unauthenticated exception while saving entity. { "timestamp": 1512077140003, "status": 500, "error": "Internal Server Error", "exception": "com.google.cloud.datastore.DatastoreException", "message": "Unauthenticated.", "path": "/users" } The error description here says the request header does not have valid authentication header, But where to place the

问题 I'm using App Engine datastore, and would like to make sure that row IDs behave similarly to "auto-increment" fields in mySQL DB. Tried several generation strategies, but can't seem to take control over what happens: the IDs are not consecutive, there seem to be several "streams" growing in parallel. the ids get "recycled" after old rows are deleted Is such a thing at all possible ? I really would like to refrain from keeping (indexed) timestamps for each row. 回答1: It sounds like you can't

问题 I am trying to learn NoSQL with Google Datastore but I am running into a problem with uniqueness. Consider an ecommerce store, it has categories and products. You do not want two products of the same SKU in the database. So I insert an entity with JSON: {"sku": 1234, "product_name": "Test product"} And it shows up with two fields. But then I can do that again and I have two or more identical products. How do you avoid this? Can you make the sku field unique? Do I need to do a query before

问题 I have an app where I am creating a large number of entities. I don't want to put them in the same entity group, because I could be creating a lot of them in a short period of time -- say 1 million in 24 hours. At certain points, I want to get all of these entities with a query like this: Foo.all() How long do I need to wait after the last Foo entity is created to be highly likely to get all of the Foo entities with this query? EDIT: From this question, it seems that I can't get all my

问题 I'm currently using Google Datastore for storing data. I want to keep an offline version in the form of sql database. Is it possible to use sqlite on google app engine to convert datastore into sql database? 回答1: No, it is not possible to use sqlite on AppEngine. Currently there is no option to convert data from the AppEngine datastore to a SQL database. 回答2: You can do this locally since Python Development Server v1.7.6 (link outdated) https://developers.google.com/appengine/docs/python

问题 When creating a results page with [Next Page] and [Prev Page] buttons, what is the cost difference between using a cursor to do this or using offset? And what are the pros and cons of each technique? As a concrete example, what is the cost of reading results 100-110. I have seen claims that offset uses "small datastore operations" and some that claim it uses a full "read operation" for each entity skipped. Using cursors, I have read that they cannot page backwards, but I noticed a new Cursor

问题 I'm getting started with Google App Engine, and I'm using Objectify. How do I create a root entity in the data store, but err if it already exists? I didn't find anything built in for this (e.g. DatastoreService.put() and therefore ofy().save() will overwrite an existing entity instead of err). The simple technique I am used to is to do this in a transaction: Err if already exists Save However, that is not idempotent; it would err in step 1 if the transaction executes twice. Here is the best

问题 I'm getting started with Google App Engine, and I'm using Objectify. How do I create a root entity in the data store, but err if it already exists? I didn't find anything built in for this (e.g. DatastoreService.put() and therefore ofy().save() will overwrite an existing entity instead of err). The simple technique I am used to is to do this in a transaction: Err if already exists Save However, that is not idempotent; it would err in step 1 if the transaction executes twice. Here is the best

问题 I've noticed that, with eventual consistency, the common form-processing workflow that I am used to (submit -> create/update record -> redirect -> reload) doesn't work. Upon redirect, the new record (probably) won't be available for display. How should I handle forms so that updates are displayed upon reload? I could try to use strong consistency, but as the App Engine documentation notes, updates are limited to one update per second. So how can I process a form providing immediate user