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

["Rick Hillegas (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DERBY-5901?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Rick Hillegas updated DERBY-5901:
---------------------------------

    Bug behavior facts: Deviation from standard,Wrong query result  (was: Wrong query result)

Marking this issue as "deviation from standard". The SQL Standard addresses the ABS case by making ABS a reserved keyword. That is, if Derby followed the Standard in this matter, then you would not be allowed to declare a user-defined function with the name ABS. The ABS case arises in Derby because Derby treats ABS as a non-reserved keyword. Changing ABS to a reserved keyword would create backward-compatibility problems.
                
> You can declare user-defined functions which shadow builtin functions by the same name.
> ---------------------------------------------------------------------------------------
>
>                 Key: DERBY-5901
>                 URL: https://issues.apache.org/jira/browse/DERBY-5901
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.10.0.0
>            Reporter: Rick Hillegas
>
> 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.

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