云数据存储区client.GetAll类型不匹配，但client.Get有效

Question

I am writing a go application in app engine that connects and returns some info from datastore entities. I'm having an issue where client.Get is working with a predefined struct but client.GetAll is throwing a type mismatch (or vice versa).

I am using the following struct with both:

type myStruct struct {
    ID              int64
    Field1          string
    Field2          string
    Release_Date    time.Time
}

This works when Release_Date is defined as time.Time (fails if int):

k := db.datastoreKey(id)
myStruct := &myStruct{}
if err := db.client.Get(ctx, k, myStruct ); err != nil {
        return nil, fmt.Errorf("datastore: %v", err)
}

func (db *datastoreDB) datastoreKey(id int64) *datastore.Key {
    return datastore.IDKey("myEntityType", id, nil)
}

This fails when Release_Date is defined as time.Time (works if int):

var myStructs []*myStruct 
q := datastore.NewQuery("myEntityType").
            Project("field1", "field2", "release_date").
            Order("field1")
keys, err := db.client.GetAll(ctx, q, &myStructs)
if err != nil {
        return nil, fmt.Errorf("datastore: %v", err)
}

The error:

datastore: cannot load field "release_date" into a "myStruct": type mismatch: int versus time.Time

(or vice versa when I swap the Release_Date definition).

Any ideas what is wrong or is this a bug?

Additional info:

I've looked at the entity dashboard and there it lists the data type as Data/Time and when I retrieve the entity with Get it loads fine into the struct and I can use the object in my code.

I have no idea why this isn't working.

Answer 1

So this isn't an elegant solution, but it's what worked for me.

What I think was the cause is that the very first entity I created had a field Release_Date of a type int but I later added entities using the type Date/Time. During my testing I had ended up removing the entity with type int for Release_Date so the only remaining entities had Date/Time. Despite having no entities with type int for Release_Date, my code failed server-side. It kept expecting that field to be of type int.

My theory is that the entity definition was established when I first created the entity and was not updated when I changed the data type later on even though no entities remained using type int.

So what I ended up doing was backing up my entities, removing ALL of them, then re-adding the entities with only Date/Time in the Release_Date field. Once I did that, everything worked fine. I still have the casing the same as shown above (i.e. my Struct uses Field but my query uses field).

This would likely be an easy thing to reproduce but I haven't gotten around to it. If anyone else gets around to testing please add a comment, otherwise I will eventually and submit a bug report.