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Cache hits for non object queries [message #515089]

Wed, 17 February 2010 16:54

No real name

Messages: 2
Registered: February 2010

Junior Member

Hello, is it possible to run queries that don't return an object against the cache?

For example a query like this that retrieves the lastnames from all Employees:

SELECT e.lastname FROM Employee e

Assume the table is cached with a full cache and a query was executed before so the cache should be fully populated. When using a ReportQuery i get an exception that report queries can not be used with CheckCacheOnly, when i use a ReadAllQuery the query returns objects instead of only the lastname values.

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Re: Cache hits for non object queries [message #515440 is a reply to message #515089]

Thu, 18 February 2010 18:57

Chris Delahunt

Messages: 1389
Registered: July 2009

Senior Member

Hello,

No, ReportQuery (which is used for queries returning non-entities) will only hit the database. The reason is likely because the cache is an object cache, and report queries just were over looked as in-memory querying was implemented - it might have just been assumed the entire object would be wanted since it is available. A feature could be filed to get EclipseLink to extract the fields from objects after running the query in-memory, but It might be more efficient to have the application run a query for the entities and then just pull the data from the returned entities directly.

Best Regards,
Chris

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