Re: Problem with objectsWithFetchSpecification
Re: Problem with objectsWithFetchSpecification
- Subject: Re: Problem with objectsWithFetchSpecification
- From: Chuck Hill <email@hidden>
- Date: Thu, 8 Sep 2005 21:00:40 -0700
Hi Ian,
On Sep 8, 2005, at 5:07 PM, Ian Joyner wrote:
Thanks Chuck and Sacha. It is completely horizontal table mapping,
so restricting qualifiers are not needed (according to p 105 of
Using EOModeler).
Yes, they are not needed. I was just wondering if you had left them
in from some past experiment and they were causing trouble.
On 09/09/2005, at 3:39 AM, Chuck Hill wrote:
On Sep 8, 2005, at 12:21 AM, Ian Joyner wrote:
I'm having a strange problem fetching from tables using
horizontal inheritance. I have a hierarchy with Skills_test at
the root and subclasses Graded_test and Value_test. Doing a fetch
on Skills_test, I expect all records in Graded_test and
Value_test to be returned. I see the SQL on the server side and
the report "9 row(s) processed, but get nothing on the server side:
NSArray /*[Skills_test]*/ tests = editingContext
().objectsWithFetchSpecification (new EOFetchSpecification
("Skills_test", null, null));
System.out.println (".load_test_tree tt " + tests.count ());
Suspecting deep fetching,
It should be deep by default.
Yes it was, I even printed out isDeep on the FS which showed true.
Sanity check: are there any PK values duplicated between the
Graded_test and Value_test tables?
There were (shouldn't they be getting separate PKs anyway). So I
reloaded the Value_test table with distinct PKs, but still it
doesn't work.
No, they should not be getting separate keys. They should be getting
keys as if all rows were in the abstract base class. The key is all
EOF has to differentiate the subclasses after they are fetches. Take
a look at an EOGlobalID. All it will show is the abstract base
entity name and the PK. EOF registers a class description (think
that is the right way to say it) against each globalID when they are
fetched. If you duplicate PKs, EOF won't be able to tell one from
the other.
Tool Curiosity: What is /*[Skills_test]*/ for. Looks like you are
using some sort of tool.
No such luck. I just document what is expected to be in the array
this way so if something weird comes out of it causing a
ClassCastException you can double check. Of course with generic
arrays, you don't have to put casts all over the place and never
get ClassCastExceptions.
Ah well, back to dreaming. :-)
I changed this to just fetch on Graded_test:
NSArray /*[Skills_test]*/ tests = editingContext
().objectsWithFetchSpecification (new EOFetchSpecification
("Graded_test", null, null));
System.out.println (".load_test_tree tt " + tests.count ());
again seeing that fetches are made to the database, but nothing
actually returned.
I then changed the fetch spec to retrieve any other table in the
database and I get the correct number of rows returned, so it
seems to be something weird with the Skills_test hierarchy. Can
anyone give a clue as to why this code is returning records from
every other table in the database except the ones I want? I'm
sure it's something strange in the model (parents are set
correctly, abstract is only on for Skills_test), but have not
been able to pinpoint what the problem is.
That is a hard one. Have you specified restricting qualifiers on
the entity in the EOModel that do not match what is in the DB? I
can't think of anything else. I'll ruminate on it for a while.
There are no qualifiers. Since all subclasses only share the
attributes name, number, and description, and all the other
attributes are completely different, I'm using horizontal mapping.
I'm sure I've just missed something really stupid, but it looks
like it's a rebuild the model problem testing every step along the
way until I find out.
I'm afraid you are correct. Something is very, very wrong but I
can't put my finger on what it would be. It is as if EOF can't
locate an entity for the rows it is fetching or is locating the wrong
entity and thus rejecting what it has fetched.
The server side definitely loads the tables:
[2005-09-09 09:54:11 EST] <WorkerThread7> evaluateExpression:
<com.webobjects.jdbcadaptor.OpenBasePlugIn$OpenBaseExpression:
"SELECT t0.GRADE_SET_KEY, t0.PARENT_TEST_KEY, t0.PRIMARY_KEY,
t0.TEST_DESCRIPTION, t0.TEST_NAME, t0.TEST_NUMBER FROM GRADED_TEST
t0">
[2005-09-09 09:54:11 EST] <WorkerThread7> 33 row(s) processed
[2005-09-09 09:54:11 EST] <WorkerThread7> evaluateExpression:
<com.webobjects.jdbcadaptor.OpenBasePlugIn$OpenBaseExpression:
"SELECT t0.BEST_SCORE, t0.LOWER_IS_BETTER, t0.PARENT_TEST_KEY,
t0.PRIMARY_KEY, t0.TEST_DESCRIPTION, t0.TEST_NAME, t0.TEST_NUMBER
FROM VALUE_TEST t0">
[2005-09-09 09:54:11 EST] <WorkerThread7> 9 row(s) processed
but the output on the client side is:
[2005-09-09 09:54:11 EST] <AWT-EventQueue-0> .load_test_tree ao1 ()
[2005-09-09 09:54:11 EST] <AWT-EventQueue-0> .load_test_tree tt 0
A couple of things to try before you rebuild the model:
1. Add an omniscient observer (see NSNotificationCenter) and see what
notifications are flying around when these rows are fetched
2. Try and do the fetch on the server in Java (the above just shows
the SQL not what happens immediately after). Can the server app
fetch OK but not the client app?
3. If you have not already done this 5,000 times, quit Xcode
andEOModeler, delete the build/ directories under the projects, start
Xcode and do a full build.
Chuck
--
Practical WebObjects - a book for intermediate WebObjects developers
who want to increase their overall knowledge of WebObjects, or those
who are trying to solve specific application development problems.
http://www.global-village.net/products/practical_webobjects
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