Re: JDOQL query problems (JPOX issues?)

[Craig L Russell]

Hi Erik,

On Oct 28, 2006, at 7:19 AM, Erik Bengtson wrote:

Michael,

I was reading Craig comments and noted that "str" is an unbound variable

Craig

The variable "str" is bound by the filter q.setFilter ("this.stringCol.contains(str)").

and not

str.

Unbound variables are not null values.

Quoting Craig L Russell <[EMAIL PROTECTED]>:

a parameter, and now I think the query is invalid since there is no value for

Hi Michael,

 From the spec,
<spec>
The candidate tuples
are the cartesian product of the candidate class and all variables
used in the result. The re-
sult tuples are the tuples of the candidate class and all variables
used in the result that sat-
isfy the filter. The result is the collection of result expressions
projected from the result
tuples.
</spec>

On Oct 27, 2006, at 2:12 PM, Michael Bouschen wrote:

Hi,

I'm having problems running JDOQL queries that group by a variable.
I think the queries below are valid, but I would like to double
check this. If you agree that the queries are valid JDOQL, I will
check the TCK to add these queries to existing TCK tests or add new
test cases. I tried the queries with JPOX version 1.1.3 and with
the nightly build from Oct 27 (no difference). I will send a test
case to reproduce the problem to Erik and Andy, since I cannot
attach archives here.

The class model is simple: pc class A has a field stringCol which
is a collection of strings and another field bCol which is a
collection of instances of class B.

The following query groups the class A instances by the strings in
their string collection:
 Query q = pm.newQuery(A.class);
 q.declareVariables("java.lang.String str");
 q.setFilter("this.stringCol.contains(str)");
 q.setGrouping("str");
 q.setResult("str");

The cartesian product of the candidate class and all variables is a
the cartesian product of all A instances and all strings contained in
any stringCol. The result tuples consist of tuples of (A, String)
where the elements of stringCol are projected and associated with the
instances of A whence they came. The result comes from grouping and
projecting the String from the result tuple. So,

This query should collect all of the unique strings in all instances
of A stringCol. The result is a List<String>. I don't know offhand
how the implementation can do this trick (returning a List<Object> in
which each element is a String is easy).

This results in an exception:
 JDOUserException: Unable to find the field "str" in the candidate
class. It is possible that this field is a field in a subclass, but
it is illegal to reference fields directly when they are in a
subclass.

I get a different exception when adding an aggregate to the result
clause
 q.setResult("str, count(this)");
 JDOUserException: Unconstrained variable referenced: str

This query should collect all of the unique strings in all instances
of A stringCol, count them, and return the string and count of
occurrences. The result is a List<Object[ ]> Each element consists of

an Object[ ] containing a String in element 0 and a Long in element 1.

  Query q = pm.newQuery(A.class);
  q.declareVariables("model.B b");
  q.setFilter("this.bCol.contains(b)");
  q.setGrouping("b");
  q.setResult("count(this), b");
This results in:
 JDOUserException: The result clause has a field expression
"UnboundVariable "UNBOUND_B.ID"" that doesnt appear in the
grouping. Any result specification has to be present in the
grouping when grouping is specified.

The behavior is different when iterating a collection of pc instances:

This query should collect all of the unique B instances in all
instances of A bCol, count them, and return the B and count of
occurrences. The result is a List<Object[ ]> Each element consists of
an Object[ ] containing a B in element 0 and a Long in element 1.

Craig

Any help is appreciated. Thanks!

Regards Michael

--
Michael Bouschen                [EMAIL PROTECTED] Engineering GmbH
mailto:[EMAIL PROTECTED]        http://www.tech.spree.de/
Tel.:++49/30/235 520-33         Buelowstr. 66
Fax.:++49/30/2175 2012          D-10783 Berlin

Craig Russell

Architect, Sun Java Enterprise System http://java.sun.com/products/ jdo

408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!

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