将Python字典序列化为Cassandra 1.2列 [英] Serialize a Python dict into a Cassandra 1.2 column

问题描述

问题

我正在尝试将序列化对象（使用cPickle）保存到Cassandra 1.2列中， python cql库。我已经尝试将列定义为文本（utf8字符串）和blob，在两种情况下，我都收到相同的错误：

该对象是Python字典：

  obj = {'id'：'sometextid'，
'time_created'：05/12/2013，＃ < ---- datetime 
'其他字符串属性'：'一些其他值'
} 
  

错误是这样的：

  raise cql.ProgrammingError（ Bad请求：％s％ire.why）
 cql.apivalues.ProgrammingError：错误请求：第31:36行字符'no'
   
 
 
然后查看执行的CQL语句，可以在腌制对象后看到一些'\'字符，例如：
 
 
 
 腌制对象的一部分 
  cdatetime 
 datetime 
 p4 
（S'\x07\xdd\x03\x1c\x000\x13\x05\xd0<'
 tRp5 
  
 我的问题 
 
 
 
使用cql库序列化python字典（包括日期时间）以将其保存到cassandra 1.2的常用方法是什么？有更好或更直接的方法吗？
 
 
 
预先感谢！
解决方案
此问题的完整解决方案是以这种方式将列定义为blob并包含十六进制编码（如cassandra文档中对blob类型的定义）：
  obj_to_store = cPickle.dumps（input_obj）.encode（ hex）
  
这样，您可以序列化常规python字典。使用常规，我的意思是它可以包含python dict可以包含的任何内容，包括日期时间或您想要的任何内容，并且可以正确地序列化并存储在cassandra中。
 
 
 
也许有更好的选择解决方案，但到目前为止，这是我发现的唯一可与任意python dict一起实际使用的解决方案。
 
 
 
希望它对某人有帮助！
 
The problem

I'm trying to save a serialized object (using cPickle) into a Cassandra 1.2 column, I'm using the python cql library. I've already tried defining the column as text (utf8 string) and blob, in both cases I'm receiving the same error:

The object is a Python dict:
obj = {'id':'sometextid',
       'time_created':05/12/2013, #<---- datetime
       'some other string property': 'some other value'
}
The error is this:
raise cql.ProgrammingError("Bad Request: %s" % ire.why)
cql.apivalues.ProgrammingError: Bad Request: line 31:36 no viable alternative at character '\'
And looking at the executed CQL statement I can see some '\' characters after pickling the object, for instance:

Part of the pickled object
cdatetime
datetime
p4
(S'\x07\xdd\x03\x1c\x000\x13\x05\xd0<'
tRp5
My questions

What is the usual way of serializing a python dict (including datetimes) to save it into cassandra 1.2 using the cql library? Is there a better or more straightforward way of doing this?

Thanks in advance!
解决方案
The complete solution to this problem is to define the column as a blob and include an encode to hex (as defined in the cassandra docs for the blob type) in this way:
obj_to_store = cPickle.dumps(input_obj).encode("hex")
In this way you can serialize a regular python dict. With regular I mean it can contain anything a python dict can, including datetimes or whatever you want and it will be properly serialized and stored in cassandra.

Maybe there is a better solution out there but so far this is the only one i've found that actually works with an arbitrary python dict.

Hope it helps somebody!

                        
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