python cassandra 创建space table并写入和查询数据

Posted 2020-09-03

 

from cassandra.cluster import Cluster

cluster = Cluster(["10.178.209.161"])
session = cluster.connect()
keyspacename = "demo_space"
session.execute("create keyspace %s with replication = {‘class‘: ‘SimpleStrategy‘, ‘replication_factor‘: 1};" % keyspacename)
# use keyspace; create a sample table
session.set_keyspace(keyspacename)

s = session
try:
    s.execute("CREATE TABLE blobbytes (a ascii PRIMARY KEY, b blob)")
except:
    pass
params = [‘key1‘, bytearray(b‘blob1‘)]
s.execute("INSERT INTO blobbytes (a, b) VALUES (%s, %s)", params)
results = s.execute("SELECT * FROM blobbytes")
print "********************"
for x in results:
    print x.a, x.b


try:
    s.execute("CREATE TABLE list_test (a ascii PRIMARY KEY, b list<blob>)")
except:
    pass
params = [‘some key here‘, [bytearray(b‘blob1‘), bytearray(b‘hello world‘)]]
s.execute("INSERT INTO list_test (a, b) VALUES (%s, %s)", params)
results = s.execute("SELECT * FROM list_test")
print "********************"
for x in results:
    print x.a, x.b

结果：

********************
key1 blob1
********************
some key here [‘blob1‘, ‘hello world‘]

最后补充：

cassandra的update和mongo的upsert效果一样！如果where的条件不满足，则会insert into！

params2 = [[bytearray(b‘blob2‘), bytearray(b‘hello world2‘)], "other key"]
s.execute("UPDATE list_test set b = b + %s WHERE a = %s", params2)
# 会直接将other key的东西插入数据库！如果other key不存在的话！

见：http://stackoverflow.com/questions/17348558/does-an-update-become-an-implied-insert