[jira] [Updated] (CASSANDRA-12923) Decimal type has inconsistent equality semantics when used in partition key

["C. Scott Andreas (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-12923?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

C. Scott Andreas updated CASSANDRA-12923:
-----------------------------------------
    Component/s: CQL

> Decimal type has inconsistent equality semantics when used in partition key
> ---------------------------------------------------------------------------
>
>                 Key: CASSANDRA-12923
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12923
>             Project: Cassandra
>          Issue Type: Bug
>          Components: CQL
>            Reporter: Branimir Lambov
>            Priority: Major
>
> Unlike {{double}} or {{float}}, for {{decimal}} used as primary key in Cassandra we have that {{3 != 3.0}} even though {{3 <= 3.0}} and {{3 >= 3.0}}:
> {code}
> cqlsh:keyspace1> create table testdec (key decimal primary key, value int);
> cqlsh:keyspace1> insert into testdec (key, value) values (3.0, 3);
> cqlsh:keyspace1> select * from testdec;
>  key  | value
> ------+-------
>   3.0 |     3
> (1 rows)
> cqlsh:keyspace1> select * from testdec where key = 3;
>  key | value
> -----+-------
> (0 rows)
> cqlsh:keyspace1> select * from testdec where key = 3.0;
>  key | value
> -----+-------
>  3.0 |     3
> (1 rows)
> cqlsh:keyspace1> select * from testdec where key >= 3 and key <= 3 ALLOW FILTERING;
>  key | value
> -----+-------
>  3.0 |     3
> (1 rows)
> {code}
> The reason for this is that we use the key's bytes (as produced by {{BigDecimal}}) to form the token:
> {code}
> cqlsh:keyspace1> select * from testdec where token(key) = token(3);
>  key | value
> -----+-------
> (0 rows)
> cqlsh:keyspace1> select * from testdec where token(key) = token(3.0);
>  key | value
> -----+-------
>  3.0 |     3
> (1 rows)
> {code}
> as well as to check key matches in [{{BigTableReader.getPosition}}|https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/io/sstable/format/big/BigTableReader.java#L217].
> The solution is to always store a canonical form of each key. In this case, such a value that the decimal's _unscaled value_ is not divisible by 10.
> This problem may be affecting other types as well.



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