关于happybase中 row_prefix 参数

标签：hbase   happybase   

起因: 使用happybase 访问hbase 时

    def scan(self, row_start=None, row_stop=None, row_prefix=None,
             columns=None, filter=None, timestamp=None,
             include_timestamp=False, batch_size=1000, scan_batching=None,
             limit=None, sorted_columns=False):

查看源码，我们能看到

        if row_prefix is not None:
            if row_start is not None or row_stop is not None:
                raise TypeError(
                    "'row_prefix' cannot be combined with 'row_start' "
                    "or 'row_stop'")

            row_start = row_prefix
            row_stop = str_increment(row_prefix)

def str_increment(s):
    """Increment and truncate a byte string (for sorting purposes)

    This functions returns the shortest string that sorts after the given
    string when compared using regular string comparison semantics.

    This function increments the last byte that is smaller than ``0xFF``, and
    drops everything after it. If the string only contains ``0xFF`` bytes,
    `None` is returned.
    """
    for i in xrange(len(s) - 1, -1, -1):
        if s[i] != '\xff':
            return s[:i] + chr(ord(s[i]) + 1)

    return None

当有如下场景 

微博表

用户ID_微博ID

假定我们想获取此用户的所有微博，在scan时就没有必要设定scan范围 ‘用户ID_0‘  ~  ‘用户ID_a‘

而可以直接使用row_prefix = ‘用户ID‘

PS：回头我会提供str_increment 的java 实现

关于happybase中 row_prefix 参数

标签：hbase   happybase   

原文地址：http://blog.csdn.net/woshiaotian/article/details/41746009