使用多个(python)客户端并行加载cassandra中的所有行

尽管如此,通过为每个计算工作者分配一个标记范围来分割大表是非常有用的.使用CQL3,它似乎可能到issue queries directly against the tokens,但是下面的python不起作用…编辑：在切换到对最新版本的cassandra数据库(doh！)进行测试后工作,并且还更新下面的每个音符的语法：

## use python cql module
import cql

## If running against an old version of Cassandra,this raises: 
## TApplicationException: Invalid method name: 'set_cql_version'
conn = cql.connect('localhost',cql_version='3.0.2')

cursor = conn.cursor()

try:
    ## remove the previous attempt to make this work
    cursor.execute('DROP KEYSPACE test;')
except Exception,exc:
    print exc

## make a keyspace and a simple table
cursor.execute("CREATE KEYSPACE test WITH strategy_class = 'SimpleStrategy' AND strategy_options:replication_factor = 1;")
cursor.execute("USE test;")
cursor.execute('CREATE TABLE data (k int PRIMARY KEY,v varchar);')

## put some data in the table -- must use single quotes around literals,not double quotes                                                                                                                                   
cursor.execute("INSERT INTO data (k,v) VALUES (0,'a');")
cursor.execute("INSERT INTO data (k,v) VALUES (1,'b');")
cursor.execute("INSERT INTO data (k,v) VALUES (2,'c');")
cursor.execute("INSERT INTO data (k,v) VALUES (3,'d');")

## split up the full range of tokens.
## Suppose there are 2**k workers:
k = 3 # --> eight workers
token_sub_range = 2**(127 - k)
worker_num = 2 # for example
start_token =    worker_num  * token_sub_range
end_token = (1 + worker_num) * token_sub_range

## put single quotes around the token strings
cql3_command = "SELECT k,v FROM data WHERE token(k) >= '%d' AND token(k) < '%d';" % (start_token,end_token)
print cql3_command

## this fails with "ProgrammingError: Bad Request: line 1:28 no viable alternative at input 'token'"
cursor.execute(cql3_command)

for row in cursor:
    print row

cursor.close()
conn.close()

理想情况下,我希望能够使用pycassa,因为我更喜欢它更加pythonic的界面.

有一个更好的方法吗？