You can let app engine choose a unique key for you or use a
transaction to first query for an existing value and then put it only
if it does not already exist. In order to do the query and put in a
transaction the entities must all be in the same Entity group which
will reduce concurrency. If you can partition your unique values
somehow (e.g. A-D, E-H...) then you can have a root entity for each
partition to decrease contention.
On 5 Feb 2010, at 17:41, smile laugh wrote:
would someone be so kind to give me an answer.
thanks
On Feb 4, 1:20 am, smile laugh <[email protected]> wrote:
I have another question.
to a unique field which cannot have same value, before I insert a
record , I must check if there is same value in the field.
it seems impossible to make the constraint in cloud platform.
because when I insert the record , maybe other one can insert the
same
record at the same time. that will break uniqueness of the field .
thanks in advance
laughsmile
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