CODEWITHSUNDEEP
pythoncassandra
TheScendant
TheScendant

Reputation: 37

Describe Cassandra ColumnFamily

I am connecting to a Cassandra database and am trying to find out what attributes an entry in a column family has. I am unable to use the cqlsh command line utility. After creating the connection I have:

myCF = ColumnFamily(myConncetion, "user")
for u in myCF.get_range():
    u_item = u[1]
    name = u_item.get('FIRST_NAME')
    print name

This prints the names of all users. I would like to know what other attributes besides "FIRST_NAME" a u_item has. Is there a built in function that can describe its attributes? Thanks in advance.

Upvotes: 1

Views: 823

Answers (1)

Aaron
Aaron

Reputation: 57748

Which version of Cassandra are you running? If you wanted to go through the table programmatically, you could try querying the schema from the system tables:

If you're on Cassandra >= 3.x+:

SELECT column_name FROM system_schema.columns 
    WHERE keyspace_name='yourkeyspacename' AND table_name='yourtablename';

If you're on Cassandra <= 2.2.x;

SELECT column_name FROM system.schema_columns 
    WHERE keyspace_name='yourkeyspacename' AND columnfamily_name ='yourtablename';

How can I execute this Select statement from a python script?

If I'm running on Cassandra 2.2.5, I can take the above code and make it work in a Python script (cassConnect.py) like this:

from cassandra.cluster import Cluster
from cassandra.auth import PlainTextAuthProvider

import sys

hostname=sys.argv[1]
username=sys.argv[2]
password=sys.argv[3]
keyspace=sys.argv[4]
table=sys.argv[5]

nodes = []
nodes.append(hostname)

auth_provider = PlainTextAuthProvider(username=username, password=password)
cluster = Cluster(nodes,auth_provider=auth_provider)
session = cluster.connect(keyspace)

pStatement = session.prepare("""
    SELECT column_name FROM system.schema_columns WHERE keyspace_name=? AND columnfamily_name=?;
""")

rows = session.execute(pStatement,[keyspace,table])
for row in rows:
    print row[0]

$ python cassConnect.py 127.0.0.1 aploetz bacon stackoverflow user
email
first
last
username

Upvotes: 1

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