[nhibernate-issues] [NHJIRA] Commented: (NH-2666) CLONE -many-to-one with property-ref makes separate select always

[Fabio M. (JIRA) <nh...@gm...>]

    [ http://216.121.112.228/browse/NH-2666?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=20945#action_20945 ] 

Fabio Maulo commented on NH-2666:
---------------------------------

If you see the resolution of NH-1583 it is Open

> CLONE -many-to-one with property-ref makes separate select always
> -----------------------------------------------------------------
>
>                 Key: NH-2666
>                 URL: http://216.121.112.228/browse/NH-2666
>             Project:  NHibernate
>          Issue Type: Bug
>          Components: Core
>    Affects Versions:  2.0.1.GA
>            Reporter: Onur Gumus
>            Priority: Major
>
> I have following tables:
>  - transactions:
>       - id (autogenerated in database); PK;
>       - numcode, for example 840 - numeric currency code;
>       - other columns
>  - currencies:
>       - id - PK, autogenerated;
>       - numcode - unique key
>       - alphacode (for example USD)
>       - decnum;
>       - fullname;
> and mapping for transactions table: 
>     <many-to-one name="numcode" column="numcode" property-ref="numcode" />
> When I'm retrieving transactions NHibernate generates a separate select for currencies table for each row from transactions table. This is very inefficient (N+1 problem).
> Solution is to do eager fetching. After specyfying eager fetching I see that transactions and currencies tables are joined, which means that I'm doing that right. However separate additional fetch in currencies is still occuring for each row in transactions table.
> I've tried both criteria API and HQL.

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