关于redis:聊聊claudb的list-command

序

本文次要钻研一下 claudb 的 list command

LeftPushCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/LeftPushCommand.java

@Command("lpush")
@ParamLength(2)
@ParamType(DataType.LIST)
public class LeftPushCommand implements DBCommand {

  @Override
  public RedisToken execute(Database db, Request request) {ImmutableList<SafeString> values = request.getParams().asList().tail().reverse();

    DatabaseValue result = db.merge(safeKey(request.getParam(0)), list(values),
        (oldValue, newValue) -> list(newValue.getList().appendAll(oldValue.getList())));

    return RedisToken.integer(result.size());
  }
}

• LeftPushCommand 实现了 DBCommand 接口，其 execute 办法提取 values，而后执行 db.merge，在 newValue.getList() 之后追加上 oldValue.getList()

LeftPopCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/LeftPopCommand.java

@Command("lpop")
@ParamLength(1)
@ParamType(DataType.LIST)
public class LeftPopCommand implements DBCommand {

  @Override
  public RedisToken execute(Database db, Request request) {List<SafeString> removed = new LinkedList<>();
    db.merge(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST,
        (oldValue, newValue) -> {ImmutableList<SafeString> list = oldValue.getList();
          list.head().stream().forEach(removed::add);
          return list(list.tail());
        });

    if (removed.isEmpty()) {return nullString();
    } else {return string(removed.remove(0));
    }
  }
}

• LeftPopCommand 实现了 DBCommand 接口，其 execute 办法执行 db.merge，它先获取 oldValue.getList()，而后取出 head 增加到 removed 中，而后再通过 list.tail() 抛弃 head 作为新的后果

RightPushCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/RightPushCommand.java

@Command("rpush")
@ParamLength(2)
@ParamType(DataType.LIST)
public class RightPushCommand implements DBCommand {

  @Override
  public RedisToken execute(Database db, Request request) {ImmutableList<SafeString> values = request.getParams().asList().tail();

    DatabaseValue result = db.merge(safeKey(request.getParam(0)), list(values),
        (oldValue, newValue) -> list(oldValue.getList().appendAll(newValue.getList())));

    return integer(result.size());
  }
}

• RightPushCommand 实现了 DBCommand 接口，其 execute 办法提取 values，而后执行 db.merge，在 oldValue.getList() 之后追加上 newValue.getList()

RightPopCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/RightPopCommand.java

@Command("rpop")
@ParamLength(1)
@ParamType(DataType.LIST)
public class RightPopCommand implements DBCommand {

  @Override
  public RedisToken execute(Database db, Request request) {List<SafeString> removed = new LinkedList<>();
    db.merge(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST,
        (oldValue, newValue) -> {ImmutableList<SafeString> list = oldValue.getList();
          list.reverse().head().stream().forEach(removed::add);
          return list(list.reverse().tail().reverse());
        });

    if (removed.isEmpty()) {return nullString();
    } else {return string(removed.remove(0));
    }
  }
}

• RightPopCommand 实现了 DBCommand 接口，其 execute 办法执行 db.merge，它先获取 oldValue.getList()，而后取出 list 倒数的 head 增加到 removed 中，而后再通过 list.reverse().tail() 抛弃 head 再 reverse 作为新的后果

ListLengthCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListLengthCommand.java

@ReadOnly
@Command("llen")
@ParamLength(1)
@ParamType(DataType.LIST)
public class ListLengthCommand implements DBCommand {

  @Override
  public RedisToken execute(Database db, Request request) {ImmutableList<SafeString> list = db.getList(request.getParam(0));
    return integer(list.size());
  }
}

• ListLengthCommand 实现了 DBCommand 接口，其 execute 办法先通过 db.getList(request.getParam(0)) 获取 list，而后返回 integer(list.size())

ListRangeCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListRangeCommand.java

@ReadOnly
@Command("lrange")
@ParamLength(3)
@ParamType(DataType.LIST)
public class ListRangeCommand implements DBCommand {

  @Override
  public RedisToken execute(Database db, Request request) {
    try {DatabaseValue value = db.getOrDefault(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST);
      ImmutableList<SafeString> list = value.getList();

      int from = Integer.parseInt(request.getParam(1).toString());
      if (from < 0) {from = list.size() + from;
      }
      int to = Integer.parseInt(request.getParam(2).toString());
      if (to < 0) {to = list.size() + to;
      }

      int min = Math.min(from, to);
      int max = Math.max(from, to);

      // TODO: use Array
      ImmutableList<SafeString> result = ImmutableList.from(list.stream().skip(min).limit((max - min) + 1));

      return convert(result);
    } catch (NumberFormatException e) {return error("ERR value is not an integer or out of range");
    }
  }
}

• ListRangeCommand 实现了 DBCommand 接口，其 execute 办法先获取 list，之后修改 min 及 max，而后取 ImmutableList.from(list.stream().skip(min).limit((max – min) + 1))

ListIndexCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListIndexCommand.java

@ReadOnly
@Command("lindex")
@ParamLength(2)
@ParamType(DataType.LIST)
public class ListIndexCommand implements DBCommand {

  @Override
  public RedisToken execute(Database db, Request request) {
    try {ImmutableList<SafeString> list = db.getList(request.getParam(0));

      int index = Integer.parseInt(request.getParam(1).toString());
      if (index < 0) {index = list.size() + index;
      }

      // TODO: fix asArray
      return string(list.asArray().get(index));
    } catch (NumberFormatException e) {return error("ERR value is not an integer or out of range");
    } catch (IndexOutOfBoundsException e) {return nullString();
    }
  }
}

• ListIndexCommand 实现了 DBCommand 接口，其 execute 办法先获取 list，而后返回 string(list.asArray().get(index))

ListSetCommand

claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListSetCommand.java

@Command("lset")
@ParamLength(3)
@ParamType(DataType.LIST)
public class ListSetCommand implements DBCommand {

  @Override
  public RedisToken execute(Database db, Request request) {
    try {int index = Integer.parseInt(request.getParam(1).toString());
      db.merge(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST,
          (oldValue, newValue) -> {ImmutableList<SafeString> oldList = oldValue.getList();
            // TODO: use Array
            List<SafeString> array = new ArrayList<>(oldList.toList());
            array.set(index > -1 ? index : array.size() + index, request.getParam(2));
            return list(array);
          });
      return status("OK");
    } catch (NumberFormatException e) {return error("ERR value is not an integer or out of range");
    } catch (IndexOutOfBoundsException e) {return error("ERR index out of range");
    }
  }
}

• ListSetCommand 实现了 DBCommand 接口，其 execute 办法先读取 index 参数，而后执行 db.merge，它读取 oldList，而后执行 array.set(index > -1 ? index : array.size() + index, request.getParam(2))，最初返回 list(array)

小结

claudb list 相干的 command 有 LeftPushCommand、LeftPopCommand、RightPushCommand、RightPopCommand、ListLengthCommand、ListRangeCommand、ListIndexCommand、ListSetCommand

doc

• command/list