Re: JDOQL query problems (JPOX issues?)

[Craig L Russell]

Hi,






Thanks,

Craig

On Oct 28, 2006, at 3:02 PM, Erik Bengtson wrote:

I think it might be useful to look at what SQL we expect to generate based on the JDOQL here. Would someone like to try the JDOQL to SQL mapping? It might help understanding of the issue.

Michael,

When compiling this query we do the following:

- define result sets
- set1 * setN (fails here since not constrained)
- restriction

We would have to change that to:

- define result sets
- restriction (this would constraint the str to stringCol)
- set1 * setN


the fastest.


on the evaluation order (unless I missed it).

Quoting Michael Bouschen <[EMAIL PROTECTED]>:

If the query was evaluated by the JDO implementation the second one is certainly I agree that this way the query should work, but needs clarification in the spec

Hi Erik,

I fully agree with Craig's description of what the queries should return.

Michael,

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

and not

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

for

str.

Yes, str is a varaible and not a parameter. But why is it unbound? There is a contains clause binding the variable to field stringCol which is a

collection of strings:
  q.setFilter("this.stringCol.contains(str)");
The third query binds the variable b to the collection of B instances
called bCol:
  q.setFilter("this.bCol.contains(b)");

Here are the three queries in single string JDOQL:

str GROUP BY str
  SELECT str, count(this) FROM A WHERE this.stringCol.contains(str)
VARIABLES String str GROUP BY str

GROUP BY b

Here is the SQL query for the second JDOQL query. Suppose class A is

= a.id GROUP BY s.text
I'm currently using this SQL query as a workaround and create a Query

the expected result!

Regards Michael

SELECT str FROM A WHERE this.stringCol.contains(str) VARIABLES String SELECT b count(this) FROM A WHERE this.bCol.contains(b) VARIABLES B b mapped to table TABLE_A and the string collection to table STRING_TABLE. This table has a foreign key to table A and a VARCHAR column called text. SELECT s.text, COUNT(a.id) FROM TABLE_A a, STRING_TABLE s WHERE s.a_id instance with the "javax.jdo.query.SQL" language parameter. It returns

Unbound variables are not null values.

Quoting Craig L Russell <[EMAIL PROTECTED]>:

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 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

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");

I'm having problems running JDOQL queries that group by a variable. check the TCK to add these queries to existing TCK tests or add new

The cartesian product of the candidate class and all variables is a

any stringCol. The result tuples consist of tuples of (A, String)

instances of A whence they came. The result comes from grouping and
projecting the String from the result tuple. So,


of A stringCol. The result is a List<String>. I don't know offhand

which each element is a String is easy).

the cartesian product of all A instances and all strings contained in where the elements of stringCol are projected and associated with the This query should collect all of the unique strings in all instances how the implementation can do this trick (returning a List<Object> in

This results in an exception:
 JDOUserException: Unable to find the field "str" in the candidate

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

class. It is possible that this field is a field in a subclass, but

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.

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

  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.

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

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

Craig

occurrences. The result is a List<Object[ ]> Each element consists of

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!

--
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!

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