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Size of @OneToMany List [message #1815951]

Tue, 15 October 2019 19:36

JeeDev_User JeeDev_User

Messages: 1
Registered: October 2019

Junior Member

Hi all,
A classic example - I have Department entity, in which exist the following association:

//bi-directional many-to-one association to Employee
@OneToMany(mappedBy="department")
private List<Employee> employees;

Now, wondering, what is the reliable way to know , how many elements that list contains ? Is it enough to just call

employees.size();

OR i need to perform TypedQuery, ie,

select count(emp) from Employee emp where department =...

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Re: Size of @OneToMany List [message #1816396 is a reply to message #1815951]

Tue, 29 October 2019 01:50

Chris Delahunt

Messages: 1389
Registered: July 2009

Senior Member

Hopefully you just tried both.

If you do, you'll find that calling collection.size() is a java operation that runs on the collection. The collection is fetched only once from the Database, so if you plan to use the collection, that might be more efficient then calling a query for the count, and then having to access the collection to fetch it from the database.

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