Question

I have an entity representing Documents that looks like this:

Document
date_creation
doc_number
doc_origin

Documents are usually referred to as ‘2012/XY/005’, that would be the fifth document in 2012 originated by XY.
So number has to be unique in the year it was created and for the same Origin, and I need to put a constraint for it.

What would be the best way to model and map this using JPA?

I think my options are:

Option 1: put another field the Document entity for the year in date creation, and make it unique(year,doc_number,doc_origin)

Option 2: create a field doc_ref and put a string like ‘YEAR/ORIG/NUMBER’ and make it unique(doc_ref)

Both options add another field duplicating the year, but Option 1 requires me to update field year consistently with date_creation and Option 2 requires me to update field doc_ref consistently with the rest, so I tend to think that Option 1 is best.

Is there another option that I am not seeing?
Thanks!

Answer 1

You could use a function-based unique index, if your database allows them. Example in Oracle:

CREATE UNIQUE INDEX YEAR_ORIGIN_NUMBER_IDX 
on DOCUMENT (TRUNC(DT_CREATION, 'YEAR'), DOC_ORIGIN, DOC_NUMBER)