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From "Daniel Fiala (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-14170) Loss of digits when doing CAST from varint/bigint to decimal
Date Wed, 17 Jan 2018 10:23:00 GMT
Daniel Fiala created CASSANDRA-14170:
----------------------------------------

             Summary: Loss of digits when doing CAST from varint/bigint to decimal
                 Key: CASSANDRA-14170
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14170
             Project: Cassandra
          Issue Type: Bug
         Environment: Tested with Cassandra 3.11.1 but this issue is present since the implementation
of cast functions.
            Reporter: Daniel Fiala


Cast functions from numeric types to decimal type are implemented as conversion to double
first and then from double to decimal: [https://github.com/apache/cassandra/compare/trunk...blerer:10310-3.0#diff-6aa4a8f76df6c30c5bb4026b8c9251eeR80].

This can cause loss of digits for big values stored in varint or bigint. It is probably unexpected
because decimal can store such values precisely.

Examples:

{{cqlsh> CREATE TABLE cast_bigint_test(k int PRIMARY KEY, bigint_clmn bigint);}}
{{cqlsh> INSERT INTO cast_bigint_test(k, decimal_clmn) VALUES(2, 9223372036854775807);}}
{{cqlsh> SELECT CAST(bigint_clmn AS decimal) FROM cast_bigint_test;}}
{{cast(bigint_clmn as decimal)}}
{{------------------------------}}
{{9.223372036854776E+18}}
{{(1 rows)}}

{{cqlsh> CREATE TABLE cast_varint_test (k int PRIMARY KEY, varint_clmn varint);}}
{{cqlsh> INSERT INTO cast_varint_test(k, varint_clmn) values(2, 1234567890123456789);}}
{{cqlsh> SELECT CAST(varint_clmn AS decimal) FROM cast_varint_test;}}
{{cast(varint_clmn as decimal)}}
{{------------------------------}}
{{ 1.23456789012345677E+18}}
{{(1 rows)}}

 



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