聊聊claudb的list command

序

本文主要研究一下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方法提取values，然后执行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方法执行db.merge，它先获取oldValue.getList()，然后取出head添加到removed中，然后再通过list.tail()丢弃head作为新的结果

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方法提取values，然后执行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方法执行db.merge，它先获取oldValue.getList()，然后取出list倒数的head添加到removed中，然后再通过list.reverse().tail()丢弃head再reverse作为新的结果

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方法先通过db.getList(request.getParam(0))获取list，然后返回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方法先获取list，之后修正min及max，然后取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方法先获取list，然后返回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方法先读取index参数，然后执行db.merge，它读取oldList，然后执行array.set(index > -1 ? index : array.size() + index, request.getParam(2))，最后返回list(array)

小结

claudb list相关的command有LeftPushCommand、LeftPopCommand、RightPushCommand、RightPopCommand、ListLengthCommand、ListRangeCommand、ListIndexCommand、ListSetCommand

doc

• command/list