code: protected Map<String, Object> prepareEntityUpdateKeyMap(BehaviorCommandMeta meta) {
          final Entity entity = extractArgumentEntity(meta); // always can get if entity update
          if (entity == null) { // no way, just in case
              return Collections.emptyMap();
          }
          final DBMeta dbmeta = entity.asDBMeta();
          final Map<String, Object> keyMap;
          final Set<String> uniqueProps = entity.myuniqueDrivenProperties();
          if (!uniqueProps.isEmpty()) {
              final Map<String, Object> uniqueMap = uniqueProps.stream().map(prop -> {
                  return dbmeta.findColumnInfo(prop);
              }).collect(Collectors.toMap(col -> col.getColumnDbName(), col -> col.read(entity)));
              keyMap = uniqueMap;
          } else if (dbmeta.hasPrimaryKey() && entity.hasPrimaryKeyValue()) {
              keyMap = dbmeta.extractPrimaryKeyMap(entity);
          } else { // no way if entity update, just in case
              keyMap = Collections.emptyMap();
          }
          return keyMap;
      }
docs: =============