[jira] [Comment Edited] (CASSANDRA-6668) Inconsistent handling of row expiration using TTL in collections

["Daniel Shelepov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-6668?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13911121#comment-13911121 ] 

Daniel Shelepov edited comment on CASSANDRA-6668 at 2/25/14 2:07 AM:
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This behaviour is by design.  Recall that UPDATEs are the same as INSERTS under the hood:
    {{UPDATE ttl_issue USING TTL 3 SET collection = _value_ WHERE id=_id_;}}
is the same as
    {{INSERT into ttl_issue (id, collection) VALUES (_id_, _value_) USING TTL 3;}}

Of course it's impossible to express append-to-set in an insert query, but that's irrelevant.  

What's important is that the second scenario can be roughly rewritten as:
   {{INSERT into ttl_issue (id, collection) VALUES (11, _some value for collection_) USING TTL 1000;}}
   {{INSERT into ttl_issue (id, collection) VALUES (11, _some other value for collection_);}}

The second statement inserts a row at id 11 at a later timestamp than the first statement.  And expiring updates are obviously not allowed to throw out updates later than themselves.  Hence in your second scenario you have a row remaining, and in the first one, you don't.


was (Author: daniels):
This behaviour is by design.  Recall that UPDATEs are the same as INSERTS under the hood:
    {{UPDATE ttl_issue USING TTL 3 SET collection = _value_ WHERE id=_id_;}}
is the same as
    {{INSERT into ttl_issue (id, collection) VALUES (_id_, _value_) USING TTL 3;}}

Of course it's impossible to express append-to-set in an insert query, but that's irrelevant.  

What's important is that the second scenario can be roughly rewritten as:
   {{INSERT into ttl_issue (id, collection) VALUES (11, _some value for collection_) USING TTL 1000;}}
   {{INSERT into ttl_issue (id, collection) VALUES (11, _some other value for collection_);}}

The second statement inserts a row at id 11 at a later timestamp than the first statement.  And expiring updates are obviously not allowed to throw out updates later to themselves.  Hence in your second scenario you have a row remaining, and in the first one, you don't.

> Inconsistent handling of row expiration using TTL in collections
> ----------------------------------------------------------------
>
>                 Key: CASSANDRA-6668
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6668
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: Apache Cassandra 2.0.3
> Apache Cassandra 1.2.8
> CQLSH client 3.1.6
>            Reporter: DOAN DuyHai
>            Priority: Critical
>
> The expiration of row when all TTLed columns have expired is inconsistent
> Scenario 1)
> {code:sql}
> cqlsh:test> create table ttl_issue(id int primary key,collection set<text>);
> cqlsh:test> update ttl_issue USING TTL 2 set collection = collection + {'test_2'} where id=10;
> cqlsh:test> update ttl_issue USING TTL 3 set collection = collection + {'test_3'} where id=10;
> cqlsh:test> select * from ttl_issue;
>  id | collection
> ----+----------------------
>  10 | {'test_2', 'test_3'}
> cqlsh:test> select * from ttl_issue;
>  id | collection
> ----+----------------------
>  10 | {'test_2', 'test_3'}
> cqlsh:test> select * from ttl_issue;
>  id | collection
> ----+------------
>  10 | {'test_3'}
> cqlsh:test> select * from ttl_issue;
> cqlsh:test> 
> {code}
>  As we can see, after a few seconds, both columns of the collection are expired. When all columns of the set have expired, the SELECT * FROM ttl_issue *returns no result, meaning that the whole row has expired.*
> Scenario 2)
> {code:sql}
> cqlsh:test> update ttl_issue USING TTL 3 set collection = collection + {'test_3'} where id=11;
> cqlsh:test> update ttl_issue USING TTL 1000 set collection = collection + {'test_1000'} where id=11;
> cqlsh:test> update ttl_issue set collection = collection - {'test_1000'} where id=11;
> cqlsh:test> select * from ttl_issue;
>  id | collection
> ----+------------
>  11 | {'test_3'}
> cqlsh:test> select * from ttl_issue;
>  id | collection
> ----+------------
>  11 | {'test_3'}
> cqlsh:test> select * from ttl_issue;
>  id | collection
> ----+------------
>  11 | {'test_3'}
> cqlsh:test> select * from ttl_issue;
>  id | collection
> ----+------------
>  11 |       null
> {code}
>  In this second scenario. We add elements to the collection with TTL but then remove one of them. *After a while, although all TTLed columns have expired, the row is till there with only the primary key present.*
>  One should expect to get the same behavior as in scenario 1), e.g. the complete row should expire.
>  I've also tried removing one element from collection using TTL 0 ({code:sql}update ttl_issue USING TTL 0 set collection = collection - {'test_1000'} where id=11;{code})  but the result is the same.
>  Quick guest: bug on row deletion marker for specific collection element append/remove ?



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