Exception for async + client
Thursday, 14 April 2016 · 4 messages · last reply 15 Apr 2016
SP
Strasser Pablo14 Apr 2016 20:33 #
Hi,
Playing with the nice new async and client library together to generate asynchronous remote query I got randomly the following exception:
java.lang.ClassCastException: org.basex.query.value.seq.tree.BigSeq
cannot be cast to org.basex.query.value.item.Item
at org.basex.query.value.ValueBuilder.concat(ValueBuilder.java:37)
at org.basex.query.expr.List.value(List.java:147)
at org.basex.query.QueryContext.value(QueryContext.java:420)
at org.basex.query.expr.If.value(If.java:131)
at org.basex.query.expr.gflwor.GFLWOR.value(GFLWOR.java:78)
at org.basex.query.QueryContext.value(QueryContext.java:420)
at org.basex.query.value.item.FuncItem.invValue(FuncItem.java:129)
at org.basex.query.func.FuncCall.invoke(FuncCall.java:87)
at org.basex.query.func.FuncCall.value(FuncCall.java:159)
at org.basex.query.value.item.FItem.invokeValue(FItem.java:45)
at org.basex.query.func.hof.HofUntil.value(HofUntil.java:27)
at org.basex.query.func.hof.HofUntil.iter(HofUntil.java:18)
at org.basex.query.QueryContext.iter(QueryContext.java:409)
at org.basex.query.expr.List$1.next(List.java:134)
at org.basex.query.MainModule$1.next(MainModule.java:123)
at org.basex.core.cmd.AQuery.query(AQuery.java:92)
at org.basex.core.cmd.XQuery.run(XQuery.java:22)
at org.basex.core.Command.run(Command.java:398)
at org.basex.core.Command.execute(Command.java:100)
at org.basex.server.ClientListener.run(ClientListener.java:136)This happen with the attached code where 10.0.0.5 is another basexserver than the current one.
The code is a preliminary test on launching system command on another basexserver asynchronously.
Have a nice evening.
Pablo
CG
Christian Grün15 Apr 2016 10:23 #
Hi Pablo,
Quoted text · Strasser Pablo · 2 lines
> java.lang.ClassCastException: org.basex.query.value.seq.tree.BigSeq cannot > be cast to org.basex.query.value.item.Item
The reason for the exception was that you were creating a huge result in your query. The input value of $result was added multiple times, resulting in a much larger result:
function ($result) {
for $id in async:ids()
return if ... else $result
}After repeated calls of this function, the length of the $result sequence exceeded many billion items and eventually got negative (because our size counter is limited to 64 bits).
See the following simplified query:
hof:until(
function ($result) { false() },
function ($result) {
for $id in 1 to 100
return $result
},
'value'
)Or this one:
fold-left(
1 to 100,
"value",
function($seq, $curr) { ($seq, $seq) }
)As the error message was not very helpful, I have added a little range check [1, 2].
Hope this helps
Christian
[1] https://github.com/BaseXdb/basex/blob/master/basex-core/src/main/java/org/basex/query/value/seq/tree/TreeSeq.java#L43-L45 [2] http://files.basex.org/releases/latest/
SP
Strasser Pablo15 Apr 2016 11:05 #
Thanks.
Helped me a lot, found the bug in my code. Tested the new version and the error message is clearer.
I don't know if its possible in case of java exception like this one to not only have the java stack trace but also the xquery one to be able to easier spot the line of code generating the error.
Have a nice day.
Pablo
Quoted text · Christian Grün · 45 lines
On 15. 04. 16 10:23, Christian Grün wrote: > Hi Pablo, > >> java.lang.ClassCastException: org.basex.query.value.seq.tree.BigSeq cannot >> be cast to org.basex.query.value.item.Item > The reason for the exception was that you were creating a huge result > in your query. The input value of $result was added multiple times, > resulting in a much larger result: > > function ($result) { > for $id in async:ids() > return if ... else $result > } > > After repeated calls of this function, the length of the $result > sequence exceeded many billion items and eventually got negative > (because our size counter is limited to 64 bits). > > See the following simplified query: > > hof:until( > function ($result) { false() }, > function ($result) { > for $id in 1 to 100 > return $result > }, > 'value' > ) > > Or this one: > > fold-left( > 1 to 100, > "value", > function($seq, $curr) { ($seq, $seq) } > ) > > As the error message was not very helpful, I have added a little range > check [1, 2]. > > Hope this helps > Christian > > [1] https://github.com/BaseXdb/basex/blob/master/basex-core/src/main/java/org/basex/query/value/seq/tree/TreeSeq.java#L43-L45 > [2] http://files.basex.org/releases/latest/
CG
Christian Grün15 Apr 2016 13:16 #
Quoted text · Strasser Pablo · 3 lines
> I don't know if its possible in case of java exception like this one to not > only have the java stack trace but also the xquery one to be able to easier > spot the line of code generating the error.
It’s a bit difficult to catch these kinds of errors, because integer overflows and out-of-memory errors can occur all over the place… Let’s see, maybe we’ll find a nice way out.
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