Creates a unique HG index on each IDENTITY/AUTOINCREMENT
column, if the column is not already a primary key.
Scope
Can only be set temporary (for a connection), for a user,
or for the PUBLIC group. Takes effect immediately.
Description
When option is set ON, HG indexes are created
on future identity columns. The index can only be deleted if the
deleting user is the only one using the table and the table is not
a local temporary table.