code: protected void bindStringColumnConstraints(Column column, PersistentProperty constrainedProperty) {
          final org.grails.datastore.mapping.config.Property mappedForm = constrainedProperty.getMapping().getMappedForm();
          Number columnLength = mappedForm.getMaxSize();
          List<?> inListValues = mappedForm.getInList();
          if (columnLength != null) {
              column.setLength(columnLength.intValue());
          } else if (inListValues != null) {
              column.setLength(getMaxSize(inListValues));
          }
      }
docs: Interrogates the specified constraints looking for any constraints that would limit the
  length of the property's value.  If such constraints exist, this method adjusts the length
  of the column accordingly.
  @param column              the column that corresponds to the property
  @param constrainedProperty the property's constraints