[nhibernate-issues] [JIRA] Created: (NH-860) Performant count of HQL query

[NHibernate J. <mik...@us...>]

Performant count of HQL query
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         Key: NH-860
         URL: http://jira.nhibernate.org/browse/NH-860
     Project: NHibernate
        Type: Improvement
  Components: Core  
    Versions: 1.2.0.Beta3    
    Reporter: Luis Ferreira


We are implementing pagination in our Web Project and we'd like to have a way of calculating the count(*) for each of the HQL queries we have already implemented *without writing specific queries for that* AND *without returning the results as a list* and then getting its count property.

A member of the team has attempted, with some success, to use NHibernate to
generate the SQL for our HQL queries and then wrapping it with a select
count(*) from (<generated SQL>). But to do that we have had to use
Reflection to access protected methods, and filling query parameters for
parametrized queries is still a problem. To really tackle the issue it would
be necessary to have some changes in NHibernate, namely public exposure in
IQuery of methods in AbstractQueryImpl / QueryImpl regarding access to named
parameters names and values.

Of course a really great solution would be for NHibernate to provide that
count(*) funcionality (in a way similar to what has been done with
projections for ICriteria? haven't used that much, we've got really hairy
queries to write). It seems to be an issue for a lot of people. For
databases that support subquerying it wouldn't be too difficult to
implement I guess, but maybe the team doesn't want to impose that kind of
restrictions.


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