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Re: BUGREPORT : OJB 1.0.5rc1 : UserAliases in OrderBy clauses are not replaced by the generated aliases for the joins resulting in illegal SQL statements Armin Waibel Mon Jul 07 17:21:23 2008

Hi Roger,

Janssen, Roger wrote:
Hi Armin,

Just to make it absolutely clear so we talk about the same thing;

When I execute a reportquery, I expect to get records back, and if I get
duplicate records back because of the joins I created, well that is
fine. But when I execute a 'normal' query, and OJB returns instantiated
objects, I would like to get a list without duplicated records.
If this just is not possible, so be it.

You can get duplicate objects back too if the order-by clause contains fields which are not part of the output columns (class fields). It's a general behavior of OJB.

For example, if I modify #ensureColumnsOrderBy and specify a order-by field/column which is not part of the output columns we get:

1.)
SELECT DISTINCT A0.ID_,A0.TITLE_,A0.VERSION_
FROM SAMPLE_BOOK A0
INNER JOIN SAMPLE_REVIEW A1 ON A0.ID_=A1.FK_BOOK
WHERE (A0.ID_ < A1.ID_) AND
A0.TITLE_ LIKE '%_testOrderBy_2_1204304719937_%'
ORDER BY A1.ID_ DESC

This doesn't work with maxDB and oracle (I suppose other DB too). As workaround OJB always adds the missing columns as "hidden" output columns. With the unmodified #ensureColumnsOrderBy method OJB will generate:

2.)
SELECT DISTINCT A0.ID_,A0.TITLE_,A0.VERSION_,A1.ID_ as ojb_col_4
FROM SAMPLE_BOOK A0
INNER JOIN SAMPLE_REVIEW A1 ON A0.ID_=A1.FK_BOOK
WHERE (A0.ID_ < A1.ID_) AND
A0.TITLE_ LIKE '%_testOrderBy_2_1204305513406_%'
ORDER BY 4 DESC

I don't know if the order-by clause in the 1. example makes sense, in the 2. example the returned result set makes sense (with ordered A1.ID_ column and duplicated A0.ID_,A0.TITLE_,A0.VERSION_ columns for each match) but the result returned by OJB ignore the ojb_col_4 and only returns A0.ID_,A0.TITLE_,A0.VERSION_.


It is always nice to have something configurable :) ... But adding a new
method to invoke different behaviour on different databases, I don't
know if that's what we all want... I am not eager to write database
dependent code... So if it is not unavoidable to prevent duplicate
records... I can live with that..

If we make it configurable you can choice which behavior of OJB you prefer (1. doesn't work with all DB, or 2. works for all DB but return unexpected duplicates).

regards,
Armin


Roger Janssen

-----Original Message-----
From: Armin Waibel [mailto:[EMAIL PROTECTED] Sent: Friday, February 29, 2008 4:56 PM
To: OJB Users List
Subject: Re: BUGREPORT : OJB 1.0.5rc1 : UserAliases in OrderBy clauses
are not replaced by the generated aliases for the joins resulting in
illegal SQL statements

Hi Roger,

Janssen, Roger wrote:
Hi Armin,

Tested what you described and the ordering seems to work in our setup as well.

What does not work however is that I get duplicate items returned. For

every match in the right-handside of the 1:N relation, I get the same object returned. Even if I execute a distinct query.


This behavior is intended by OJB. OJB adds all "unknown fields/columns" to the query statement. See SqlQueryStatement#ensureColumnsOrderBy.

If you change this method in the same way like #ensureColumnsGroupBy
works, the fields won't be added and you won't get duplicate items.

This works with e.g. mysql but doesn't work for e.g. maxDB, oracle -
they always expect an output column in the order-by clause.
So, I don't know how to solve this issue? Should we make this
configurable e.g. Query.addMissingOrderByColumns(boolean enable)?


Also the setPathOuterJoin functionality does not work. Inner joins keep being generated. After this latest info from you I tried the same

with the setPathOuterJoin :

        query.setPathOuterJoin("myAlias");

And

      query.setPathOuterJoin("myAlias.collectionAttr");

But no luck.

ok I will try to setup some tests too.

regards,
Armin

Greetings,

Roger Janssen
iBanx

-----Original Message-----
From: Armin Waibel [mailto:[EMAIL PROTECTED]
Sent: Wednesday, February 27, 2008 2:51 PM
To: OJB Users List
Subject: Re: BUGREPORT : OJB 1.0.5rc1 : UserAliases in OrderBy clauses

are not replaced by the generated aliases for the joins resulting in illegal SQL statements

Hi Roger,

I start work on OJB-137 (your issue) and noticed while "playing" with order-by tests that the following notations seems to work (class Book has a 1:n relation to class Review):

Criteria c1 = new Criteria()
.addEqualTo("reviews.summary", "3_review" + name); c1.setAlias("alias_1"); Criteria c2 = new Criteria() .addEqualTo("reviews.summary", "4_review" + name); c2.setAlias("alias_2"); c1.addAndCriteria(c2); ReportQueryByCriteria q

= QueryFactory.newReportQuery(Sample.Book.class,
c1, true);
q.setAttributes(new String[]{"id", "title","reviews.id"}); q.addOrderByDescending("alias_2.reviews.id");

If I prefix the path expression with the user alias it seems to work ("alias_2.reviews.id" instead of "alias_2.id"). Did you tried this
too?
regards,
Armin


Armin Waibel wrote:
Hi Roger,

I create two new "user-alias" related bug reports:

http://issues.apache.org/jira/browse/OJB-137

https://issues.apache.org/jira/browse/OJB-139

OJB-137 reflects your issue. Locally I fixed OJB-139 (easier to fix then
137) and start work on OJB-137 (seems more complex to fix).

regards,
Armin

Armin Waibel wrote:
Hi Roger,

now I get your point (I'm a bit slow on the uptake ;-)). I start writing many new "order by" tests to isolate the problem and to make

sure that changes don't have unrequested side-effects.

> itself was not stable enough for us). In fact, I helped implementing > this feature in OJB a long time ago, and I believe the documentation > on > the OJB site is the documentation I once sent to you guys.

You are right, I found your example in the query documentation. But I can't find a test in the OJB test-suite. I think this is the reason why this feature got lost between 1.0.rc6 and now (the criteria/query
stuff was reworked/improved since 1.0rc6).

My new tests show another bug when using a user alias on a 1:n relation with table-per-subclass inheritance - but this is another story. After finish test writing, I will do my best to find a patch for your problem and keep you up-to-date.

regards,
Armin

Janssen, Roger wrote:
Hi,

The management summary answer to your question "is it important to support alias-names in order by and having clause" is : Yes, it is really really really important!!!

So now for some background information explaining our situation.

We implemented a concept to support non-modelled (abstract)
attributes.
We need to support many different complex forms and datasets for our customers. The deviation between customers is huge, so modifying our domain model (and thus our pojos and thus out database tables) for every customer implementation is not an option. We need to have a stable core domain model.

So all our objects in our domain model have a collection property that is capable of holding a collection of abstract-attribute instances, it's a standard 1:N relation which OJB supports. Abstract attribute classes are classes implementing name-value tuples, the name of the attribute, and the value of the attribute. So adding new attributes to specific objectclass instances implies we just have to add abstract attribute instances to the collection and OJB will store them in the apropriate table in the database. We do not have to modify our domain model by adding new java properties to the affected classes and adding new columns to the affected tables.

So querying for values of object properties, represented by abstract attributes, we need to create clauses combining the name/value properties of the abstract attribute instances.

So an example query with two selection criteria based on abstract attributes of an object could be:

SELECT * FROM PERMIT AS A0 INNER JOIN PERMIT_ABSTRACT_ATTRIBUTE AS
A1 INNER JOIN PERMIT_ABSTRACT_ATTRIBUTE AS A2 WHERE A0.ID=A1.ID AND

A0.ID=A2.ID AND
(A1.NAME='<name of attribute 1> AND A1.VALUE='<value of attribute
1>') AND
(A2.NAME='<name of attribute 2> AND A2.VALUE='<value of attribute
2>');

Since we need to work with bounded name/value pairs, we need to bind
them together using a alias, in this example the aliases are A1 and
A2.
So if we want to order the resultset on such an abstract attribute value the query would look like:

SELECT * FROM PERMIT AS A0 INNER JOIN PERMIT_ABSTRACT_ATTRIBUTE AS
A1 INNER JOIN PERMIT_ABSTRACT_ATTRIBUTE AS A2 WHERE A0.ID=A1.ID AND

A0.ID=A2.ID AND
(A1.NAME='<name of attribute 1> AND A1.VALUE='<value of attribute
1>') AND
(A2.NAME='<name of attribute 2> AND A2.VALUE='<value of attribute
2>')
ORDER BY A2.VALUE;

We need to use the alias to link the orderby to the proper join, of

which there are two, to the same join table (the abstract attribute

table)!

This is rather common functionality, currently supported in all our

applications, supported by OJB 1.0rc6 that we use (the 1.0 release itself was not stable enough for us). In fact, I helped implementing this feature in OJB a long time ago, and I believe the documentation
on the OJB site is the documentation I once sent to you guys.

The upcoming 1.0.5 release has some features that we have been waiting for, for several years. We have been able to postpone improvements in our applications for this long, but we cannot do this any longer. So we really need these new features 1.0.5 implements, but we need the user-alias in the orderby to work as well, otherwise we will loose a lot of functionality and our
customers will not accept that.
Some of the required features are the native limit-clause implementations, the reference descriptor implementation without using foreign-keys (I requested this feature for more then a year ago myself), etc., etc.. I hope you now have an understanding of how we use this feature, and
that we cannot afford to loose it.

Greetings,

Roger Janssen
iBanx
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