带有过滤器的AppEngine数据存储区查询从不返回结果（Go）

Question

If I don't use a filter, I get results. If I use a filter (this record definitely exists), I don't get any results. It might be the lack of an index defined for that property, but, as I understand it, simple indices should automatically be created in the development server (and an index.yaml file created and populated with it). This is not happening.

query = datastore.NewQuery("UserAccount").Filter("email =", "[e-mail]")

ua := UserAccount{}
t := query.Run(ctx)
for ; ; {
    if _, err = t.Next(&ua); err == nil {
        log.Debugf(ctx, "Current: %s", ua)
    } else if err == datastore.Done {
        break
    } else {
        panic(err)
    }
}

When the development server terminates, it states that it's "saving search indexes":

INFO     2016-08-08 05:09:52,894 api_server.py:651] Saving search indexes

However, since an "index.yaml" file doesn't appear, I'm assuming that no indices needed to be created, which means that my query must not've had the desired effect?

What am I missing?

Edit:

Note that the record was previously created and the application stopped and started many times since. I sincerely doubt this is a eventual-consistency thing.

Edit 2:

For the purpose of testing, I've created the following model with the following code. They both exhibit the same behavior as my original model and code.

Definition:

type TestEntity struct {
    Email string
}

Code:

log.Debugf(ctx, "Putting.")

email := "anothertest@a.b"

te := &TestEntity{
        Email: email,
}

k := datastore.NewKey(ctx, "TestEntity", "123", 0, nil)
_, err = datastore.Put(ctx, k, te)
if err != nil {
    panic(err)
}

log.Debugf(ctx, "Waiting.")
time.Sleep(1 * time.Second)

query := datastore.NewQuery("TestEntity")

var results []TestEntity
_, err = query.GetAll(ctx, &results)
log.Debugf(ctx, "GetAll: %s", results)

log.Debugf(ctx, "Running query.")

query = datastore.NewQuery("TestEntity").Filter("email =", email)

te = &TestEntity{}
t := query.Run(ctx)
for ; ; {
    if _, err = t.Next(te); err == nil {
        log.Debugf(ctx, "Found: [%s]", te.Email)
    } else if err == datastore.Done {
        log.Debugf(ctx, "Done.")
        break
    } else {
        panic(err)
    }
}

Results:

2016/08/09 02:11:36 DEBUG: Putting.
2016/08/09 02:11:36 DEBUG: Waiting.
2016/08/09 02:11:37 DEBUG: GetAll: [{anothertest@a.b}]
2016/08/09 02:11:37 DEBUG: Running query.
2016/08/09 02:11:37 DEBUG: Done.

Screenshot of Viewer:

Answer 1

The property name in the datastore is "Email" with capital E, not "email".

It's case-sensitive, must be queried with capital E:

query = datastore.NewQuery("UserAccount").Filter("Email =", "[e-mail]")

If you would want it to be saved / retrieved with small e, you could use tags to do the mapping, e.g.:

type UserAccount struct {
    Email string `datastore:"email"`
    // other fields...
}