public static TableDescriptorBuilder enable(TableDescriptorBuilder builder) throws IOException {
    if (!builder.hasCoprocessor(ConstraintProcessor.class.getName())) {
      builder.setCoprocessor(ConstraintProcessor.class.getName());
    }
    return builder;
  }
Enable constraints on a table.
<p/>
Currently, if you attempt to add a constraint to the table, then Constraints will automatically
be turned on.
hbase-server/src/main/java/org/apache/hadoop/hbase/constraint/Constraints.java