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Date: Fri, 9 Dec 2011 16:43:39 +0000 (UTC)
From: "Rick Curtis (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (OPENJPA-2068) Improve performance of
 java.util.Calendar fields
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    [ https://issues.apache.org/jira/browse/OPENJPA-2068?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13166293#comment-13166293 ] 

Rick Curtis commented on OPENJPA-2068:
--------------------------------------

The code I committed doesn't have the quirk where you'll get a proxied instance when you issue a query where you only are selecting a Calendar field. Also, this behavior isn't configurable as it is transparent.
                
> Improve performance of java.util.Calendar fields
> ------------------------------------------------
>
>                 Key: OPENJPA-2068
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-2068
>             Project: OpenJPA
>          Issue Type: Improvement
>          Components: jdbc
>    Affects Versions: 2.2.0
>            Reporter: Rick Curtis
>            Assignee: Rick Curtis
>             Fix For: 2.2.0
>
>         Attachments: OPENJPA-2068.patch
>
>
> While doing some performance testing, I've found that we could improve the performance of loading Entities that have java.util.Calendar fields. When loading the data into a Calendar field, we actually create two Calendar instances per field. Normally creating an extra instance wouldn't be that big of a deal, but since creating a Calendar is very expensive I would like to remove creation of the extra instance.
> The call flow is something like this:
> - em.find(...) // find an Entity which has a calendar field
> ... execute query, processing result set...
> - DBDictionary.getCalendar(ResultSet,...) // Here we pull a Timestamp out of the result set, and create an unproxied Calendar instance.
> ...
> // now while trying to store the Calendar into the Entity instance, we find that this type needs to be proxied. 
> SingleFieldManager.proxy(...) // Here we create the second Calendar instance, which is a proxied calendar
> I'd like to add a configuration property to DBDictionary that tells the runtime to always create proxied calendar instances. This would remove the creation of the initial un-proxied instance. For a large majority of application which use Calendars this would help. 
> As always, there is a catch to this approach. If you were to execute a query such as : em.createQuery("SELECT c.myCal FROM CalendarEntity c where c.id=:id", MyCalendar.class), you would get back a proxied instance. This shouldn't be that big of a deal... but still a bit of a quirk.

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