Specifing the index through annotation is not in the Public Draft of JPA
2.0 and I do not expect it to be part of the Specification. The only way
to specify index currently is to provide a "columnDefinition" to the
@Column annotation.
When designing a database one should consider the DDL generation of JPA to
be a helpful tool. DDL generation from JPA should not be considered a
replacement for thorough database design.