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https://issues.apache.org/jira/browse/CASSANDRA-6668?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13911121#comment-13911121
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Daniel Shelepov edited comment on CASSANDRA-6668 at 2/25/14 2:09 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 for this bug.
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 than 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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