Null objects in lists with gaps in indexes

[wyd...@gmail.com]

Given the following collection mapping in an hbm mapping file:

    <class name="Parent" table=" ParentTable">

        <id name="ID" column="ID" type="Int32" unsaved-value="0">

            <generator class="identity" />

        </id>

        <list name="SomeChildCollection" table=" SomeChildTable  " lazy="true" access="nosetter.camelcase-underscore">

            <key column="ParentTableID" />

            <list-index column="SequenceIndex"" />

            <element column="SomeTextField" type="String" length="50" />

        </list>

If, somehow, the values of SequenceIndex includes a gap (let's say, for a specific ParentTableID of 20, there are records in SomeChildTable with a SequenceIndex of 0, 1, and 5), NHibernate will fill the collection with null objects for each one of the index values missing:   object, object, null, null, null, object

Why?

How do I stop this?

Granted, I don't specifically WANT there to be gaps.  If there is a gap, it must be some sort of data or concurrency issue.  But I also don't actually CARE if there are gaps.  I just want the SeqienceIndex field to indicate order.  From a business logic perspective of my application, gaps or no gaps makes no difference.  I just don't want null objects in my collection.

I am using the list-index field to sort the fields in order, like if I were using <bag order-by="SequenceIndex"> but where I want NHibernate to update the index field instead of me dealing with it by hand.

Is this considered a feature?  Will this ever be changed?