| Re: [eclipselink-users] Lazying-loading and Collection.size() |
Normally if a collection is too big for you to ever desire loading it, you should not map it. Just query it instead. cowwoc wrote: > > In other words, it will retrieve the entire resultset and dump it into > memory? Is there a way to perform the following operations efficiently? > > 1) get the size of the collection > 2) retrieve an element at index X > > all of this without retrieving the entire collection from the database and > (ideally) without issuing queries explicitly. > > Gili > > > James Sutherland wrote: >> >> size() will instantiate lazy collections in EclipseLink and any other JPA >> implementation that I know of. I'm not sure the JPA spec says anything >> about it. >> >> >> >> cowwoc wrote: >>> >>> Hi, >>> >>> What does the JPA standard (and alternatively EclipseLink) say about >>> Lazy Loading and Collection/Set/List.size()? If the collection hasn't >>> been initialized yet, does size() simply invoke a count(*) query or does >>> it retrieve the entire collection including its elements? >>> >>> I'm thinking of the following use-case: >>> >>> 1) int size = myList.size(); >>> 2) Object randomElement = myList.get((int) (Math.random() * size)); >>> >>> What is guaranteed to happen under the hood according to JPA and >>> according to EclipseLink? Ideally I want to pass a Collection around my >>> API, instead of forcing it to be Query-aware and issue SQL statements >>> explicitly. >>> >>> Thank you, >>> Gili >>> >> >> > > ----- --- http://wiki.eclipse.org/User:James.sutherland.oracle.com James Sutherland http://www.eclipse.org/eclipselink/ EclipseLink , http://www.oracle.com/technology/products/ias/toplink/ TopLink Wiki: http://wiki.eclipse.org/EclipseLink EclipseLink , http://wiki.oracle.com/page/TopLink TopLink Forums: http://forums.oracle.com/forums/forum.jspa?forumID=48 TopLink , http://www.nabble.com/EclipseLink-f26430.html EclipseLink Book: http://en.wikibooks.org/wiki/Java_Persistence Java Persistence -- View this message in context: http://www.nabble.com/Lazying-loading-and-Collection.size%28%29-tp19581000p19629289.html Sent from the EclipseLink - Users mailing list archive at Nabble.com.