[CASSANDRA-8824] cassandra python driver return None when querying static column on partition bigger than 5000 entites

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Duplicate
• Severity: Normal
• Assignee: Unassigned
• Reporter: Mateusz Moneta
• Created: 18/Feb/15 12:54
• Updated: 16/Apr/19 09:31
• Resolved: 18/Feb/15 14:09

Description

When we querying partition with static column that has more than 5000 entities some of them has unset static value, however when querying by cqlsh everything is fine.

Here is example, expire is a static column, folder_id is primary key.

cqlsh> select id, parent_id, expire, mtime from share.entity where folder_id='68f2af3a2d1e4f95a231d5cb47e57cf2' and mtime < '2015-02-01 06:21:25+0000';

 id                               | parent_id | expire                   | mtime
----------------------------------+-----------+--------------------------+--------------------------
 68f2af3a2d1e4f95a231d5cb47e57cf2 |      null | 2015-02-22 10:51:27+0000 | 2015-02-01 06:21:24+0000

cqlsh> select count(*) from share.entity where folder_id='68f2af3a2d1e4f95a231d5cb47e57cf2';
 count
-------
  5547

In [1]: from django.db import connection

In [2]: ses = connection.connection.session

In [3]: from cassandra.query import SimpleStatement

In [13]: query = "select * from share.entity where folder_id='68f2af3a2d1e4f95a231d5cb47e57cf2'";

In [14]: st = SimpleStatement(query)

In [15]: c, d = 0, 0

In [16]: for e in ses.execute(st):
    if e['expire'] is None:
        c += 1
    else:
        d += 1

In [17]: c
Out[17]: 547

In [18]: d
Out[18]: 5000

After further digging its turned out that this is a problem with fetch_size param and this can be easily reproduced:

In [1]: from cassandra.query import SimpleStatement

In [2]: from django.db import connection

In [3]: ses = connection.connection.session

In [4]: ses.execute(SimpleStatement("create table t (k text, s text static, i int, primary key(k, i));"))

In [5]: for i in range(1, 500):
   ....:     ses.execute(SimpleStatement("insert into t (k, i) values ('k', %d);" % i))

In [6]: c, d = 0, 0

In [7]: for e in ses.execute(SimpleStatement("select * from t", fetch_size=100)):
    if e['s'] is None:
        c += 1
    else:
        d += 1
   ....:         

In [8]: c
Out[8]: 400

In [9]: d
Out[9]: 100

Issue Links

• duplicates: CASSANDRA-8502 Static columns returning null for pages after first