Db4o select random objects
Does anyone know how to select random objects from a Db4o开发者_Python百科 db?
I think the best way is this. Run a query and get the result as IList. Since the returned list lazy-loads the object (at least in embedded-mode) you can pick random objects by the index.
Something like this:
public static ICollection<T> RandomObjects<T>(IList<T> objectSet, int amount)
{
var resultSet = new HashSet<T>();
var random = new Random();
amount = Math.Min(objectSet.Count, amount);
while (resultSet.Count<amount)
{
resultSet.Add(objectSet[random.Next(amount)]);
}
return resultSet;
}
And then use it:
IList<Person> potentialObjects = container.query(Person.class);
ICollection<Person> randomObject = RandomObjects(potentialObjects,10);
Another possibility would be to build a LINQ-Query which randomly matches. However such a query cannot be optimized, so could perform badly.
var random = from Person p in dbc
where new Random().Next(2) == 1
select p;
Edit: Changed to C#
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