[Hibernate-issues] [Hibernate-JIRA] Closed: (HB-160) Batch Reading

[<leg...@at...>]

Message:

   The following issue has been closed.

   Resolver: Gavin King
       Date: Sat, 9 Aug 2003 8:43 AM

This was already implemented.
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View the issue:

  http://opensource.atlassian.com/projects/hibernate/secure/ViewIssue.jspa?key=HB-160


Here is an overview of the issue:
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        Key: HB-160
    Summary: Batch Reading
       Type: New Feature

     Status: Closed
   Priority: Minor
 Resolution: DUPLICATE

    Project: Hibernate2
 Components: 
             core
   Fix Fors:
             2.1 beta 1
   Versions:
             2.0.1

   Assignee: 
   Reporter: Christian Bauer

    Created: Tue, 8 Jul 2003 3:39 PM
    Updated: Sat, 9 Aug 2003 8:43 AM

Description:
Feature is used to reduce # queries sent to the database to retrieve related lazily
initialized 1-1's.  Example:  Retrieve 20 Contact objects, each has a 1-1 to an Account. 
Initial Query just asked to retrieve the Contact objects with nothing else being built
initially.  If each Contact works for a different Account, then if I call getAccount on each
Contact (with initially empty cache), what started as 1 query turns into 21 queries (one PK
query for each Account).
 
 Feature supports the ability for those lazy Account references to "remember" what their
"originating query" was - the one used to retrieve the 20 Contact objects in the first
place.  Then, when the first Contact's "account" reference is initialized, it joins with the
originating query's criteria to get all of the related accounts that match the originating
query's criteria, populating the cache with 20 Account objects with one query.  Now, what
would otherwise be 21 queries is now just 2 (1 for the 20 Contacts, and 1 for the 20
Accounts).
 
 Example:
 
 originating query:  select * from contact where last_name = 'Smith'
 
 Then, when the first uninitialized Contact.account reference is initialized (from that set
of Contacts), the account query is:
 
 select t0.* from account t0, contact t1 where t1.account_id = t0.account_id and
t1.last_name = 'Smith'


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