Monday, December 13, 2010

Removing rows from a Query Collection

Here's a link to a blog that describes how to remove Rows from a query Collection without deleting the row from the database.  This works for entity based views but I had a need to remove rows from a Query Collection of a non-entity based read only view.     The way I did this was to add a transient attribute "Displayed" to the view.  I then create a view criteria (filterCriteria) that filters out any row where Displayed='False'.  In the "Edit View Criteria" dialog I set the Query Execution Mode to "In Memory"   After executing the query in my backing bean I loop through the rows and set the Displayed attribute to 'False" for any row I don't want to display.   Then I apply an in-memory filter by executing the following


Normally you would just filter the original results using SQL but in my case the rules for determining which rows to remove did not translated easily to SQL so this technique was employed.  This might be useful if you were filtering out rows based on the users permissions and those permissions were stored in LDAP and couldn't be made part of the query.

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