Division operator may give wrong results with NUMERIC operands
--------------------------------------------------------------
Key: DERBY-1139
URL: http://issues.apache.org/jira/browse/DERBY-1139
Project: Derby
Type: Bug
Components: SQL
Versions: 10.1.2.1
Reporter: Matthias Ohlemeyer
Priority: Critical
The division operator '/' may give wrong results when used with NUMRERIC
operands.
Example (copied from ij):
CREATE TABLE t (d1 DOUBLE, d2 DOUBLE, n1 NUMERIC(31,11), n2
NUMERIC(31,11));
INSERT INTO t VALUES (1.5, 2.5, 1.5, 2.5);
SELECT d1/d2, n1/n2, n1*(1.0/n2) FROM t;
1 |2 |3
----------------------------------------------------------------
0.6 |0 |0.600000000000000000000000000000
1 row selected
The result in column 2 should not be zero, but 0.6.
It seems there is something wrong with the calculation of the scale. Hint from
Satheesh Bandaram:
If you look at NumericTypeCompiler code, which calculates the scale and
precision of operation result type, the comments and the code doesn't seem to
match. (getScale() method):
NumericTypeCompiler.java
else if (TypeCompiler.DIVIDE_OP.equals(operator))
{
/*
** Take max left scale + right precision - right scale + 1,
** or 4, whichever is biggest
*/
LanguageConnectionContext lcc = (LanguageConnectionContext)
(ContextService.getContext(LanguageConnectionContext.CONTEXT_ID));
// Scale: 31 - left precision + left scale - right scale
val = Math.max(NumberDataValue.MAX_DECIMAL_PRECISION_SCALE - lprec
+ lscale - rscale, 0);
}
Here val is returning zero for scale, it seems.
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://issues.apache.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see:
http://www.atlassian.com/software/jira
