Hi,

I have an Entity with a List of @Embedded objects.

@Entity
class Entity
    @Embedded
    List<SomethingEmbedded> elements

class SomethingEmbedded
     String name;
     String id;

How can I query to get an element in the embedded array by, lets say id
attribute.
I want the query to return only "SomethingEmbedded", without the "Parent"
Entity object, since the "elements" can have thousands of elements and I do
not need all the parent object, only on element on elements list.

Is it possible with Morphia/Mongo ?

Thanks in advance for your help.

You may want to follow these issues:
http://jira.mongodb.org/browse/SERVER-828
http://jira.mongodb.org/browse/SERVER-1264
http://jira.mongodb.org/browse/SERVER-142

Understood.

In you opinion is this something I should take into account when designing
my datamodel ? For example making the arrays that I expect to grow as
entities rather than embedded objects ?

Thanks in advance.

As an alternative is there a way to return the parent object with the
embedded array with only one element, the one I was searching for ? Lack of
support of this kind of queries kinda makes embedding of large arrays a
total no-go.

Storing constantly growing entities can have a large performance
penalty in terms of IO because of the way in-place updates work. Each
time you grow an entity it must first try to update the existing
document in-place, but in the case where the new one is too big to fit
in the allocated space, then it must move it to a new location (while
padding the size of the new allocation for future growth) and update
all the indexes pointing to it. If you do this a lot it could increase
the IO costs for each write operation; the result of this may be that
more write-heavy users should steer away from this pattern if the read
frequency isn't enough to justify the additional write costs.

Using Morphia on a project and it has been great thus far so thanks
for all the work!

I am having trouble making this query in Morphia.  Can some tell me
how to run a complex $elemMatch

db.BaseActivity.find(
{ "_id" : ObjectId("4d4a19cc93fb69115e88e82c") ,
         "rs" : { "$elemMatch"  :
                    { "_id" : ObjectId("4d4a1d0fdda16911f16ac0ac") ,
                     "l" : { "$nin" : [ 127]}}
         }

Can this query be done using Morphia?  I know how to generate it with
only the _id filter but how can I do both?

*Sample query for only one attribute:
Query updateQuery = ds.createQuery(parent.getClass()).filter("_id",
parent.getId());

Thanks!

updateQuery.filter("rs elem", BasicDBObjectBuilder.start("_id",
objId).push("I").add("$nin",
Collections.singletonList(127)).pop().get());

(it is something like that; I haven't tested that.)

On Feb 6, 2:04 am, Scott Hernandez <scotthernan...@gmail.com> wrote:

Hi,

Is there a way to execute query by example using Morphia?

Something like:

User exampleUser = new User("em...@ddd.com");
User realUser = ds.createQuery(User.class).filter("this",
exampleEntity).get();

I'm thinking something like:

ds.QBE(exampleUser).get/asList()

Is QBE a good method name, or maybe "queryByExample"?