About collection

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Forum
23

Optimistic locking: prevent version increment on entity collection attribute

Hello, I have an entity E with an attribute which is a collection of entities (one to many ... the increment of the version of entity E when entities are added to or removed from the collection ... If it is a bidirectional relationship that is owned by the entities in the collection (i.e. the collection
Forum
22

Query to search for common elements in two separate collections.

I'm trying to work out the most efficient way to build a query that can compare two collections ... is to use some sort of hash function for the collections and to retrieve candidate collections by identical hash code. Candidate collections should then be further filtered by checking for equality. The hash
Forum
21

Using Scala collections with ObjectDB

Hi, I cannot see that it is possible to make scala collection classes persistable within ObjectDB ... .collection._  api for it to work ? (http://www.scala-lang.org/docu/files/collections-api/collections.html)   /Peter   You are right - Scala collections require some special handling, which is not
Forum
21

collection of embedded objects

1. In general, are there any restrictions of the use of @Embedded objects in collections, compared to @Entity? 2. If you have a large nested collection of @Embedded objects, and you remove the parent @Entity, does the remove cascade through the whole collection? 3. Is searching through collections
Forum
21

Custom collection types

Hi   In our project in few places there are used collections from emf framework eg EcoreEMap http ... , nevertheless it causes some questions. I checked that i can easily change the type of collection between ... of this classes but only their content so I suppose that you treat collections some how differently. Can i
Forum
21

Lazy Init / Eager / Join Fetch collection strategy ? What to choose ?

Hello, I'm doing some tests to choose the best collection fetch strategy. I have entities with many lazy collections and i don't want to load them all. (depends on context) In JPA / Hibernate world ... seems to be more efficient than only fetch required collections. Can you confirm my observations ? To finish, wake
Forum
21

PersistenceManager.getObjectsById(Collection,boolean) throwing JDOException

I have a call to getObjectsById(Collection,boolean) that is throwing a JDOException the first time ... why this might occur? We're using ObjectDB 2.2.4_02. The collection being passed in is a HashSetcollection
Forum
21

No clue how to query with collection

getStreet();     int getStreetNo(); } @Entity class Contact {     Collection
collection with a concatenated value of street + streetNo (if not ... that selecting the first item of a collection ain't be a good idea. now I can select the right item
Manual
20

Retrieving JPA Entity Objects

collection and map persistent fields (i.e. through one-to-one and many-to-one relationships ... through non collection and map persistent fields are also retrieved. Theoretically, in some extreme ... ) private Employee manager; : } The default for non collection and map references is FetchType
Forum
20

Fetching Collections Puzzle

(which is recommended anyway to improve performance). Paul,   As posted above your collection ... to go and retrive the first element of the collection. This will only work if you are within a transaction ... from Node n left outer join fetch n.children where ....." this will also fetch your collection