Method override missing from DataValueFactory interface
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Key: DERBY-4062
URL: https://issues.apache.org/jira/browse/DERBY-4062
Project: Derby
Issue Type: Sub-task
Reporter: Bryan Pendleton
Assignee: Bryan Pendleton
Priority: Minor
I believe the problem involves o.a.d.iapi.types.DataValueFactory.
This interface defines dozens and dozens of overloads of the method
getDataValue(), for lots of different combinations of datatypes.
For most of the Java "boxed" types (Short, Long, Float, Double, etc.),
DataValueFactory defines a pair of getDataValue() methods. For example,
here are the method pair that the interface defines for Short:
/**
* Get a SQL smallint with the given value. A null argument means get
* a SQL null value. The second form uses the previous value (if
non-null)
* to hold the return value.
*
*/
NumberDataValue getDataValue(Short value);
NumberDataValue getDataValue(Short value, NumberDataValue
previous)
throws
StandardException;
HOWEVER, for the Integer type, DataValueFactory doesn't define both overloads,
but only defines the 'previous'-style overload:
/**
* Get a SQL int with the given value. A null argument means get
* a SQL null value. Uses the previous value (if non-null)
* to hold the return value.
*
*/
NumberDataValue getDataValue(Integer value, NumberDataValue
previous)
throws
StandardException;
The actual implementation, in o.a.d.iapi.types.DataValueFactoryImpl, though,
does implement both the Integer overloads. But this method is NOT present
in the DataValueFactory interface:
NumberDataValue getDataValue(Integer value);
Because this method is not present in the interface, code such as
row.setColumn(SYSXPLAIN_RESULTSET_NO_OPENS, dvf.getDataValue(no_opens));
which the code anticipates will invoke the above method, instead calls the
method
public UserDataValue getDataValue(Object value);
which has a very different behavior (instead of returning a SQLInteger, it
returns a UserType).
This accidental invocation of the wrong implementation method was causing data
corruption
errors in regression tests for the DERBY-2487 patch, which uses the above
setColumn call.
Instead of inserting SQLInteger values into the system table, the code was
inserting
java.lang.Integer UserType values; since those values don't match the defined
type of
the column(s) in the system catalog, the table appeared to be corrupt.
I believe that this problem never affects external Derby applications, but only
internal Derby code,
as the DataValueFactory interface is an internal interface only. Still, since
it appeared to
cause data corruption and invalid query results, it is potentially a quite
serious problem.
See this thread in the derby-dev archives for a bit more discussion:
http://mail-archives.apache.org/mod_mbox/db-derby-dev/200902.mbox/%[email protected]%3e
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