The column 'Currency_ID' has already been added in this SQL builder (Parameter 'columnName')

[NikitaEgorov]

My legacy project has very strange DB Scheme :)
Base table Items and all object inherit from this table for example

class Currency : Items{}
In DB: table Items and table Currencies
But Id from Currencies reused as Id for localization as Caption 🤬
And I get this HBM and exception

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
  <class xmlns="urn:nhibernate-mapping-2.2" dynamic-update="true" name="Domain.Currency, Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="Items">
    <id name="Id" type="System.Int32, System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e" unsaved-value="0">
      <column name="Item_ID" not-null="true" />
      <generator class="identity" />
    </id>
    <property name="Guid" type="System.Guid, System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e">
      <column name="Item_Guid" />
    </property>
    <property name="Version" type="System.Int64, System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e">
      <column name="Item_Version" />
    </property>
    <join table="Currencies">
      <key>
        <column name="Currency_ID" />
      </key>
      <property name="Code" type="System.String, System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e">
        <column name="Currency_Code" />
      </property>
      <many-to-one cascade="none" class="Domain.Caption, Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Caption">
        <column name="Currency_ID" />
      </many-to-one>
    </join>
  </class>
</hibernate-mapping>

and NHibernate 5.3.8
Exception: The column 'Currency_ID' has already been added in this SQL builder (Parameter 'columnName')

   at NHibernate.SqlCommand.SqlInsertBuilder.AddColumnWithValueOrType(String columnName, Object valueOrType)

[NikitaEgorov]

   at NHibernate.SqlCommand.SqlInsertBuilder.AddColumnWithValueOrType(String columnName, Object valueOrType)
   at NHibernate.SqlCommand.SqlInsertBuilder.AddColumns(String[] columnNames, Boolean[] insertable, IType propertyType)
   at NHibernate.Persister.Entity.AbstractEntityPersister.GenerateInsertString(Boolean identityInsert, Boolean[] includeProperty, Int32 j)
   --- End of inner exception stack trace ---
   at NHibernate.Persister.Entity.AbstractEntityPersister.GenerateInsertString(Boolean identityInsert, Boolean[] includeProperty, Int32 j)
   at NHibernate.Persister.Entity.AbstractEntityPersister.PostInstantiate()
   at NHibernate.Persister.Entity.SingleTableEntityPersister.PostInstantiate()
   at NHibernate.Impl.SessionFactoryImpl..ctor(Configuration cfg, IMapping mapping, Settings settings, EventListeners listeners)
   at NHibernate.Cfg.Configuration.BuildSessionFactory()
   at FluentNHibernate.Cfg.FluentConfiguration.BuildSessionFactory()

[NikitaEgorov]

if add insert="false" name="Caption" update="false" to <many-to-one cascade="none" class="Domain.Caption, Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Caption">
All is working fine

[hazzik]

Hi @NikitaEgorov this is a documented possible breaking change in 5.2.0

nhibernate-core/releasenotes.txt

Lines 624 to 629 in d2599c6

	##### Possible Breaking Changes #####
	* Entities having many non-readonly properties (including many-to-one) mapped to
	the same column will no more silently ignore the trouble till an insert or update
	is attempted. They will now cause the session factory built to fail. When
	mapping many properties to the same column, all of them excepted at most one
	should be mapped with `insert="false" update="false"`.

The solution you have found is exactly what is recommended.