I have "Table per class hierarchy" mapping using discriminator column.

I need to create unique constraint that should consists of two columns: a property column and discrimonator column (unique property for given class).

Does it possible to do this via hibernate mapping, or I should write custom ddl-sqcript?

Doesn't look like its possible. According to the docs you can create unique constraints over multiple _properties_ using <properties> and property-ref but <properties> doesn't allow <discriminator>.

You can include custom ddl in your mapping files however, through the <database-object> element:
e.g. (from docs)

Thanks for relpy. Will try <database-object>