Using a Set cannot help - they still need to be read into memory and
adding to a set will still replace an existing equal entry.
So at the lowest level, you still need to do a read before your write
if you want to avoid clobbering existing data with the same key.
On 19 Jan 2010, at 03:08, Rusty Wright wrote:
In your class, if you have a Collection of entities that you want to
not have duplicates you can make it a Set, and be sure that you've
provided a proper equals() and hashCode() for your entities;
specifically, do not include the primary key because it starts out
null when you instantiate the entity, and then is set after the
entity is persisted. I don't know if there is anything on the JDO
or DataNucleus site that explains this but I do remember reading
about it in either a Hibernate book or on the Hibernate site.
tal wrote:
How do I enforce a unique constraint in GAE?
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