/**
  * Gets the {@link mondrian.rolap.aggmatcher.Recognizer.Matcher} for this foreign key column name.
  *
  * @param foreignKeyName Name of a foreign key column
  */
 public Recognizer.Matcher getForeignKeyMatcher(String foreignKeyName) {
   Recognizer.Matcher matcher = foreignKeyMatcherMap.get(foreignKeyName);
   if (matcher == null) {
     // get default AggRule
     DefaultDef.AggRule rule = getAggRule();
     DefaultDef.ForeignKeyMatch foreignKeyMatch = rule.getForeignKeyMatch();
     matcher = foreignKeyMatch.getMatcher(foreignKeyName);
     foreignKeyMatcherMap.put(foreignKeyName, matcher);
   }
   return matcher;
 }