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PODoes NHibernate Criteria API support projections on collection properties?
 

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  1. PODoes NHibernate Criteria API support projections on collection properties?
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    <p>I need to replicate the following working HQL query using criteria API.</p> <pre><code>session.CreateQuery( "select c " + "from Parent p " + "inner join p.Children c " + "where p.Id = 9 " + "and c.Id = 33") .SetMaxResults(3) .List(); </code></pre> <p>The query selects all the children that satisfy a certain criteria that belong to parents that satisfy another criteria. In my example both criterion are simple Id equalities but they could be anything.</p> <p>For some reason the equivalent criteria API query returns a list with the right number of items but those items are all null.</p> <pre><code>session.CreateCriteria(typeof (Parent)) .Add(Restrictions.Eq("Id", 9)) .CreateCriteria("Children") .Add(Restrictions.Eq("Id", 33)) .SetProjection(Projections.Property("Children")) .SetMaxResults(3) .List(); </code></pre> <p>Why don't these two queries return the same results?</p> <p>Here is the generated SQL from the HQL query:</p> <pre><code>SELECT TOP 3 childid7_, name7_ FROM (SELECT children1_.childid AS childid7_, children1_.name AS name7_, Row_number() OVER(ORDER BY current_timestamp) AS __hibernate_sort_row FROM dbo.parent parent0_ LEFT OUTER JOIN dbo.child children1_ ON parent0_.parentid = children1_.parentid WHERE (parent0_.parentid = 9) AND (children1_.childid = 33)) AS QUERY WHERE QUERY.__hibernate_sort_row &gt; 0 ORDER BY QUERY.__hibernate_sort_row </code></pre> <p>And here is the SQL from the Criteria API query:</p> <pre><code>SELECT TOP 3 y0_ FROM (SELECT this_.parentid AS y0_, Row_number() OVER(ORDER BY current_timestamp) AS __hibernate_sort_row FROM dbo.parent this_ INNER JOIN dbo.child child1_ ON this_.parentid = child1_.parentid WHERE this_.parentid = @p0 AND child1_.childid = @p1) AS QUERY WHERE QUERY.__hibernate_sort_row &gt; 0 ORDER BY QUERY.__hibernate_sort_row </code></pre> <p>Note that the join between parent and child is unidirectional. The child entity does not have a reference property pointing to its parent.</p> <p>Can anybody suggest an alternative that would allow me to work around this limitation?</p>
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    1. USNathan Baulch
    1. USNathan Baulch
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    1. COWhy is there child1_.childid > @p1 in the query from the criteria API?
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      1. USStefan Steinegger
    2. COOops, that should be an equals.
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      1. USNathan Baulch
 

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