问题
I want to build GQL query to get an object using its numeric id. I'm doing this in Datastore viewer in App management console, so I can't use Model.get_by_id(numeric_id). Something like
SELECT * FROM Model WHERE id = <numeric_id>
also doesn't work.
回答1:
Try this:
SELECT * FROM Model where __key__ = KEY('Model', <numeric_id>)
回答2:
Unfortunately, there does not appear to be a way to write a query equivalent to
SELECT * FROM Model WHERE id = <numeric_id>
which would select all Model entities with the given id. If you're ok with something equivalent to
SELECT * FROM Model WHERE id = <numeric_id> AND parent IS NULL
you can use something like
SELECT * FROM Model where __key__ = KEY('Model', <numeric_id>)
If your entity does have a parent though, you'll need to specify that as part of the key, like
SELECT * FROM Model where __key__ = KEY('ParentModel', <parent_name_or_id>, 'Model', <numeric_id>)
If the parent itself has a parent, you'll need to specify that too. (Grandparent goes left of the parent, and so on.)
Of course if you're not restricted to GQL (like if you're using Python, Go, or Java), you can query the keys, decode them and filter by id, then fetch the corresponding entities. But of course that doesn't work in the Datastore Viewer since you can only use GQL.
回答3:
Another way around is, first get the key for the entity using the id by
key = db.Key.from_path('Model', int(id))
then get the object by
obj = db.get(key)
The advantage is, you do not have to do any string formatting.
reference: problem set 3 at this course, https://classroom.udacity.com/courses/cs253/
回答4:
I was getting this error:
GQL Query error: Encountered ... at line 1, column 42. Was expecting one of: UNQUOTED_NAME ... QUOTED_NAME ..."
It turns out that in the Google AppEngine datastore developer's admin console, you should drop the quotes and use something like this:
SELECT * FROM MyEntity WHERE __key__ = Key(MyEntity, 5695872079757312)
回答5:
In my case I had to change the type of ID from String to Long
来源：https://stackoverflow.com/questions/3869858/gql-query-with-numeric-id-in-datastore-viewer