Python Cassandra - 保存文件给出 "Invalid STRING constant"

Question

我是 Cassandra 的新手，我想使用 python-cassandra 驱动程序将一些小文件保存到数据库中，但出现“无效的字符串常量”错误。

表:

cqlsh:testkeyspace> desc table files_uuids;

CREATE TABLE files_uuids (
  id uuid,
  file blob,
  PRIMARY KEY ((id))
) WITH
  bloom_filter_fp_chance=0.010000 AND
  caching='KEYS_ONLY' AND
  comment='' AND
  dclocal_read_repair_chance=0.100000 AND
  gc_grace_seconds=864000 AND
  index_interval=128 AND
  read_repair_chance=0.000000 AND
  replicate_on_write='true' AND
  populate_io_cache_on_flush='false' AND
  default_time_to_live=0 AND
  speculative_retry='99.0PERCENTILE' AND
  memtable_flush_period_in_ms=0 AND
  compaction={'class': 'SizeTieredCompactionStrategy'} AND
  compression={'sstable_compression': 'LZ4Compressor'};

和 Python 代码:

>>> from cassandra.cluster import Cluster
>>> cluster = Cluster()
>>> session = cluster.connect('testkeyspace')
>>> import os, uuid
>>> file = os.path.join(os.getcwd(), 'file.txt')
>>> fid = uuid.uuid4()
>>> with open(file, 'rb') as f:
...   data = f.read()
...   session.execute("INSERT INTO files_uuids (id, file) values (%s, %s)", (fid, data))
...
Traceback (most recent call last):
  File "<stdin>", line 3, in <module>
  File "/usr/local/lib/python2.7/dist-packages/cassandra/cluster.py", line 1405, in execute
    result = future.result(timeout)
  File "/usr/local/lib/python2.7/dist-packages/cassandra/cluster.py", line 2976, in result
    raise self._final_exception
cassandra.InvalidRequest: code=2200 [Invalid query] message="Invalid STRING constant (text
) for file of type blob"

我做错了什么？

Python 2.7、Cassandra 2.0。

Answer 1

知道了... data = f.read() 是 str() (message="无效的字符串常量 [...]).

所以这会起作用:

>>> with open(file, 'rb') as f:
...   data = f.read()
...   res = bytearray(data)
...   session.execute("INSERT INTO files_uuids (id, file) values (%s, %s)", (fid, res))

结果:

cqlsh:testkeyspace> select * from files_uuids;

 id                                   | file
--------------------------------------+--------------
 6a918341-c3d9-48a1-96fe-9a4b2bc6ea51 | 0x746578740a