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https://issues.apache.org/jira/browse/DERBY-5901?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13838714#comment-13838714
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Knut Anders Hatlen commented on DERBY-5901:
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In the approach used in DERBY-6362, it means that the SQL text of a CHECK
constraint is expanded before it is put into a column in SYS.SYSCHECKS. That
is, if you execute "create table(x int, check(x < sin(pi())))", it would
previously store 'check(x < sin(pi()))' in SYS.SYSCHECKS.CHECKDEFINITION, and
now it will store 'check(x < "SYSFUN"."SIN"("SYSFUN"."PI"()))' instead.
We could do the same with the SQL text that we put into
SYS.SYSTRIGGERS.TRIGGERDEFINITION, SYS.SYSTRIGGERS.WHENCLAUSETEXT,
SYS.SYSVIEWS.VIEWDEFINITION and SYS.SYSCOLUMNS.COLUMNDEFAULT. As an extra
bonus, it will also solve DERBY-6370 for us.
> 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: 10.10.1.1
> Reporter: Rick Hillegas
> Labels: derby_triage10_10
>
> 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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