When a user expand a table node, it should be possible to see what column is a primary key of this table.
We can do it with some additional symbols against this column, like (pk) for example.
For example column "id" is the primary key and we can show "id (pk)" in the DB explorer tree.
Then when user expands table, it is clear that "id" is the primary key of this table.
Reassigned to new owner.
This works in netbeans 7.2: The icon marks the primary key columns with a different color highlight (normal color blue, primary key is marked red).