Google Cloud Datastore更新实体：Node.js客户端

Question

How to update GCP datastore entity in nodejs.

// Saves the entity
datastore
.save(task)
.then(() => {
  console.log(`Saved ${task.key.name}: ${task.data.description}`);
})
.catch(err => {
 console.error('ERROR:', err);
});

Usually save function is storing the data and if we send the existing the data it is updating fine. But if we miss some columns then it is nullifying those columns. Is there any function to update entity in datastore.

Answer 1

save() in datastore overwrites the entity. If you want to do an update :

1. Get the entity.
2. update the relevant fields in the entity.
3. use save() to update.

To avoid race conditions, datastore transaction can be used

Answer 2

What I understand is that you are confused about why updating an entity with, say 8 valid properties, will have 2 properties nulled if you only provide 6/8 properties in the update.

This is by design as Datastore will write the entire entity with save() . What you want to do is force save(method=upsert, yourdata) , and a shortcut is to use the upsert() method.

Answer 3

reading the "save" documentation at https://cloud.google.com/nodejs/docs/reference/datastore/1.3.x/Datastore -

By default, all properties are indexed. To prevent a property from being included in all indexes, you must supply an excludeFromIndexes array.

I assume that you get null fields because they're indexed. try to remove indexes from fields that may not exist.

Answer 4

If you use gstore-node there is an update() method on the Model that does this for you.
gstore will do (in a transaction):

• Get the entity in the Datastore
• Merge the data you pass with the entity fetched
• save the entity back in the Datastore.

Here is the documentation of the update() on Model: https://sebelga.gitbooks.io/gstore-node/content/model/update-method.html