Hi! I'm working with PostgreSQL to create some data types written in C.

For example, I have: typedef struct Point3D { char id[50]; double x; double y; double z;
} Point3D;

The input and output functions are working properly.

But the problem is the following: Every id of Point3D must be unique (and can be NULL), so I have decided to create an unique index on this field id, but is that possible?

I'm thinking in something like this: create unique index test_point3d_idx on test_point3d (( getID(columname) )); where getID returns the field ID of columname.

But I need to implement getID and I am really blocked.

Any advice?