Creating dynamically named fields in requires a Transformer

I needed to index multiple fields from a table dynamically. At first it didn't work, reading the field name as "_t". Out of curiosity, I added a transformer declaration to the entity. This gave me the list of fields I needed.

Why did adding a transformer that is never used fix my problem? Removing the transformer declaration causes the problem to come back, and it does not matter which transformer I declare.

I am running Solr 4.1, and this issue first happened to me on the included example-DIH example that came with the download. I read the Solr reference guide for 4.0, and could not find a reason why adding a transformer made it work.

Below is the db-data-config.xml file:

 
    <dataConfig>
	<dataSource name="foo" driver="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost/foo"  user="fakeadmin" password="fakepass"/>
	<document>
		<entity name="products" query="select * from `product`">
			<field name="id" column="id" />
			<entity name="names" query="select * from names where productId = '${products.id}'" transformer="LogTransformer">
				<field name="${names.fieldName}_t" column="fieldValue"/>
			</entity>
		</entity>
	</document>
</dataConfig>