Bugs item #2815820, was opened at 2009-07-02 16:30
Message generated for change (Comment added) made by stmane
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=482468&aid=2815820&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: PF/compiler
Group: MonetDB4 "stable"
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Hans (hans_0_)
Assigned to: Nobody/Anonymous (nobody)
Summary: PF: Endless loop in innocent xquery
Initial Comment:
OS: Fedora core 10
Installed rpms version x.28.4
While executing the innocent looking xquery listed below with mclient the
result is endless.
The message: "!ERROR: xquery_print_result_main: operation failed." is shown
after a while.
When removing one of the two elements within element result the result is
small and as expected.
The situation happened in a real life situation and was reduced to this small
xquery.
let $result :=
<document xid="5">
<folder xid="6">
<file xid="19">
<slack xid="20">
<properties>
<stream xend="507" xstart="544"/>
<streamname>#data</streamname>
<name>aap</name>
</properties>
</slack>
<properties>
<md5>xxx</md5>
<sha1>yyy</sha1>
<stream xend="123" xstart="456"/>
<streamname>data</streamname>
<name>noot</name>
</properties>
</file>
</folder>
<properties>
<type>doc</type>
</properties>
</document>
let $notedobjectsresult := for $notedxid in ("20","5")
return $resu...@xid=$notedxid]
let $subresult := $notedobjectsresult
let $nobj := count($subresult)
let $out := (
for $i in (1 to $nobj)
let $raw := exactly-one($subresult[$i])
return element { name($raw) } {
$raw/properties/(name|stream)
}
)
return element result {
element attributes { for $a in distinct-values(for $j in $out/@* return
name($j)) return element { $a } {} },
element results { $out }
}
<>
Regards,
Hans.
----------------------------------------------------------------------
>Comment By: Stefan Manegold (stmane)
Date: 2009-07-02 20:12
Message:
If I recall correctly from abroad, we recently changed (fixed) the
implementation/semantics of grouped aggregations to return NIL (NULL) for
empty groups.
Hence, the only alternative to your ifthenelse() work-around would be to
(re-)introduce "non-nil" alternative of the grouped aggregates (next to the
current "nil"-default ones) that would use a fixed (or parameterized)
non-nil "default" value for empty groups ...
Greetings from a "MonetDB-dominated" SIGMOD 2009 in Providence, RI!
(;-))
----------------------------------------------------------------------
Comment By: Jan Rittinger (tsheyar)
Date: 2009-07-02 17:37
Message:
I cooked down the problem to the following XQuery snippet:
let $out := (
for $a in (<a x="5"/>)[...@x=("5","20")]
return <b>{ $a/xxx }</b>
)
return <c>{ $out/@*, $out }</c>
The problem is that '{sum}(empty_bat, bat_with_one_row)' that calculates
the size for node b returns a single row with a nil value in the tail. This
invalid size is added to the document representation and the serialization
interprets it incorrectly.
@MIL experts: Is there a nice solution to use a default value for {sum} or
do I need to add the following additional check?
res := {sum}(..., ...);
res := [ifthenelse]([isnil](res), res.project(0), res);
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=482468&aid=2815820&group_id=56967
------------------------------------------------------------------------------
_______________________________________________
Monetdb-bugs mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/monetdb-bugs
