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From "Alex Petrov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-12829) DELETE query with an empty IN clause can delete more than expected
Date Wed, 30 Nov 2016 15:20:58 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-12829?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15708858#comment-15708858
] 

Alex Petrov commented on CASSANDRA-12829:
-----------------------------------------

Thanks for noticing this. Turns out that my code did same thing, just was much more complex
to parse. Your suggestion is very good. 

As regards {{IN}} restriction, it's all quite simple to fix. However, I see a bit inconsistency.
{{IN}} with just one value is simplified to {{EQ}} relation. {{IN}} with more than 1 value
or 0 values will remain {{IN}}. And because {{IN}} restrictions are not supported with conditional
deletions, currently we'll disallow {{0}} and {{> 1}} values, while {{1}} value will work
just as {{EQ}}. 

Do you think such behaviour would be acceptable? Are empty IN restrictions actually useful
or will just cause edge-cases and unclear behaviour?

> DELETE query with an empty IN clause can delete more than expected
> ------------------------------------------------------------------
>
>                 Key: CASSANDRA-12829
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12829
>             Project: Cassandra
>          Issue Type: Bug
>          Components: CQL
>         Environment: Arch Linux x64, kernel 4.7.6, Cassandra 3.9 downloaded from the
website
>            Reporter: Jason T. Bradshaw
>            Assignee: Alex Petrov
>
> When deleting from a table with a certain structure and using an *in* clause with an
empty list, the *in* clause with an empty list can be ignored, resulting in deleting more
than is expected.
> *Setup:*
> {code}
> cqlsh> create table test (a text, b text, id uuid, primary key ((a, b), id));
> cqlsh> insert into test (a, b, id) values ('a', 'b', 00000000-0000-0000-0000-000000000000);
> cqlsh> insert into test (a, b, id) values ('b', 'c', 00000000-0000-0000-0000-000000000000);
> cqlsh> insert into test (a, b, id) values ('a', 'c', 00000000-0000-0000-0000-000000000000);
> cqlsh> select * from test;
>  a | b | id
> ---+---+--------------------------------------
>  a | c | 00000000-0000-0000-0000-000000000000
>  b | c | 00000000-0000-0000-0000-000000000000
>  a | b | 00000000-0000-0000-0000-000000000000
> (3 rows)
> {code}
> *Expected:*
> {code}
> cqlsh> delete from test where a = 'a' and b in ('a', 'b', 'c') and id in ();
> cqlsh> select * from test;
>  a | b | id
> ---+---+--------------------------------------
>  a | c | 00000000-0000-0000-0000-000000000000
>  b | c | 00000000-0000-0000-0000-000000000000
>  a | b | 00000000-0000-0000-0000-000000000000
> (3 rows)
> {code}
> *Actual:*
> {code}
> cqlsh> delete from test where a = 'a' and b in ('a', 'b', 'c') and id in ();
> cqlsh> select * from test;
>  a | b | id
> ---+---+--------------------------------------
>  b | c | 00000000-0000-0000-0000-000000000000
> (1 rows)
> {code}
> Instead of deleting nothing, as the final empty *in* clause would imply, it instead deletes
everything that matches the first two clauses, acting as if the following query had been issued
instead:
> {code}
> cqlsh> delete from test where a = 'a' and b in ('a', 'b', 'c');
> {code}
> This seems to be related to the presence of a tuple clustering key, as I could not reproduce
it without one.



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