Bugs item #1960373, was opened at 2008-05-08 18:08
Message generated for change (Comment added) made by stmane
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=482468&aid=1960373&group_id=56967
Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: Core
Group: MonetDB Common 1.24
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Sjoerd Mullender (sjoerd)
Assigned to: Peter Boncz (boncz)
Summary: kunion and nil
Initial Comment:
mil>var a := new(void,oid).append(oid(nil)).append([EMAIL PROTECTED]).tunique();
mil>a.info().find("hkey").print();
[ "1" ]
mil>var b := kunion(a,a);
mil>b.info().find("hkey").print();
[ "1" ]
mil>b.print();
#-----------------#
# h t # name
# oid void # type
#-----------------#
[ nil, nil ]
[ [EMAIL PROTECTED], nil ]
[ nil, nil ]
If run with debugmask 10, BATpropcheck complains about b having hkey set.
The questions are:
- is tunique right in setting hkey, even in the presence of a nil?
- is kunion right in producing three values (since nil != nil)?
- is kunion right in setting hkey (again since nil != nil)?
- is BATpropcheck right in complaining that hkey is set (since nil = nil, or
perhaps because hkey should never be set in the presence of nils)?
----------------------------------------------------------------------
>Comment By: Stefan Manegold (stmane)
Date: 2008-08-26 09:51
Message:
Logged In: YES
user_id=572415
Originator: NO
so, the semantics of NIL is
- in case of select and join (I guess/hope):
NIL is not compareable to NIL; hence the result of comparing NIL to NIL
is never TRUE (but actually not FALSE either)
- in case of [tk]unique:
NIL is comparable to NIL and the result of comparing NIL to NIL is TRUE
?
Shouldn't try to find a single consistent semantic for NILs?
----------------------------------------------------------------------
Comment By: Peter Boncz (boncz)
Date: 2008-08-26 09:35
Message:
Logged In: YES
user_id=591107
Originator: NO
tunion is right in setting hkey
Kunion is wrong in producing three results and in setting hkey.
Batpropcheck is right in complaining about it.
My answer is based on the historical situation where nil is just another
value; that is before giving nil special treatment in select and join.
----------------------------------------------------------------------
Comment By: Stefan Manegold (stmane)
Date: 2008-08-26 09:20
Message:
Logged In: YES
user_id=572415
Originator: NO
See also
[ 2075180 ] the unique column can't insert more than 1 row with null
http://sourceforge.net/tracker/index.php?func=detail&aid=2075180&group_id=56967&atid=482468
----------------------------------------------------------------------
Comment By: Sjoerd Mullender (sjoerd)
Date: 2008-06-05 16:22
Message:
Logged In: YES
user_id=43607
Originator: YES
Peter, I'd like you to give your opinion on this issue.
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=482468&aid=1960373&group_id=56967
-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Monetdb-bugs mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/monetdb-bugs
