[DERBY-5901] You can declare user-defined functions which shadow builtin functions by the same name.

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 10.10.1.1
• Component/s: SQL
• Labels: derby_triage10_10
• Urgency: Normal
• Issue & fix info: Repro attached
• Bug behavior facts: Deviation from standard, Wrong query result
• Assignee: Unassigned
• Reporter: Richard N. Hillegas
• Created: 13/Aug/12 14:33
• Updated: 09/Apr/14 11:30

Description

You can override a Derby builtin function by creating a function with the same name. This can give rise to wrong results.

Consider the following user code:

public class FakeSin
{
public static Double sin( Double input )

{ return new Double( 3.0 ); }

}

Now run the following script:

connect 'jdbc:derby:memory:db;create=true';

values sin( 0.5 );

create function sin( a double ) returns double language java parameter style java no sql external name 'FakeSin.sin';

values sin( 0.5 );
values sin( 0.5 );

Note the following:

1) The first invocation of sin() returns the expected result.

2) You are allowed to create a user-defined function named "sin" which can shadow the builtin function.

3) The second invocation of sin() returns the result of running the builtin function. This is because the second invocation is character-for-character identical to the first, so Derby just uses the previously prepared statement.

4) But the third invocation of sin() returns the result of running the user-defined function. Note that the third invocation has an extra space in it, which causes Derby to compile it from scratch, picking up the user-defined function instead of the builtin one.

Issue Links

• is related to: DERBY-6370 dblook doesn't schema-qualify identifiers in trigger actions
• is related to: DERBY-672 Re-enable user defined aggregates