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https://issues.apache.org/jira/browse/DERBY-4251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12727232#action_12727232
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Andrew McRae commented on DERBY-4251:
-------------------------------------
The most relevant fact is that the vast majority of Java database code already
running in the real world was written according to JDBC spec 3.0 or earlier
versions. What I would like you to think about and ask yourself is "What is the
most relevant JDBC specification for Derby?"
Consider that Derby still (thankfully) runs on Java 1.4 - thus allowing it to
work in the widest possible range of Java runtimes already out there. The
current JDBC api version at the time JRE 1.4 was released (2003) until Java 6
came out (2008) was JDBC 3.0 as defined in the JDBC 3.0 spec (December 2001)
and the Java 1.4 API Javadoc.
Here's what the spec says about compliance:
--8<------8<----
JDBC 3.0 API Compliance
A driver that is compliant with the JDBC 3.0 API must do the following:
* Comply with the JDBC 2.0 API requirements
* Include the following required interfaces:
java.sql.ParameterMetaData
java.sql.Savepoint
...
--8<------8<----
Here's the Java 1.4 API:
http://java.sun.com/j2se/1.4.2/docs/api/java/sql/ResultSet.html#getRow()
--8<------8<----
getRow
public int getRow()
throws SQLException
Retrieves the current row number. The first row is number 1, the second
number 2, and so on.
Returns:
the current row number; 0 if there is no current row
Throws:
SQLException - if a database access error occurs
Since:
1.2
--8<------8<----
This is the behaviour required by over 5 years of software developed throughout
the IT industry. There is no point in claiming to support later versions of the
JDBC specification if Derby does not support the JDBC 2.0 API.
Here is what the JDBC 4.0 spec says about the goals of the 4.0 specification:
--8<------8<----
8. Maintain backward compatibility with existing applications and drivers
Existing JDBC technology-enabled drivers ( JDBC drivers) and the
applications
that use them must continue to work in an implementation of the Java
virtual
machine that supports the JDBC 4.0 API. Applications that use only features
defined in earlier releases of the JDBC API will not require changes to
continue
running. It should be straightforward for existing applications to migrate
to
JDBC 4.0 technology.
--8<------8<----
The latest JDBC documentation has added a new comment saying getRow() is
optional for the special case of forward-only result sets, but clearly by the
above reasoning this is self-contradictory to the goals of JDBC 4.0 as stated
by Sun, and so should be ignored. The getRow() method has never been optional
and by the chain of logic going back to JDBC 2 it cannot become optional.
Let me explain this in a different way in case it has not become clear.
Specification compliance is not a matter of being cool, it's a matter of being
practically useful due to fully functional interoperability. The more recent
the spec the software supports then the more features it will support and the
cooler it will be, but not at the expense of breaking compatibility with the
older specifications because that would make it useless to most existing
software. (That would also be very uncool.)
This issue is not a request for a feature enhancement as you have now
incorrectly recategorised it.
This is a bug, it is a nonconformance to the JDBC 2.0 API, and Derby must
comply with that API for three reasons:
1) to allow all existing Java software to use Derby (assuming you do actually
want people to use Derby), and
2) to merit compliance with BOTH the JDBC 3.0 and JDBC 4.0 specifications, and
3) to be cool.
This makes sense to me. What does everyone else think?
> Make Derby EmbedResultSet support getRow() for FORWARD_ONLY result sets
> ------------------------------------------------------------------------
>
> Key: DERBY-4251
> URL: https://issues.apache.org/jira/browse/DERBY-4251
> Project: Derby
> Issue Type: Improvement
> Components: JDBC
> Affects Versions: 10.4.2.0, 10.5.1.1
> Environment: Windows XP, and Java 6 or Java 1.4.2
> Reporter: Andrew McRae
> Original Estimate: 2h
> Remaining Estimate: 2h
>
> According to source of the Derby version I first found it in, and the version
> just released today, here is the offending code:
> https://svn.apache.org/repos/asf/db/derby/code/tags/10.5.1.1/java/engine/org/apache/derby/impl/jdbc/EmbedResultSet.java
> {quote}
> public int getRow() throws SQLException {
> // getRow() is only allowed on scroll cursors
> checkScrollCursor("getRow()");
> /*
> * * We probably needn't bother getting the text of * the
> underlying
> * statement but it is better to be * consistent and we aren't
> * particularly worried * about performance of getRow().
> */
> return theResults.getRowNumber();
> }
> {quote}
> The comment and the check for scrollability is incorrect. The Javadoc comment
> for this getRow is a duplicate of the Sun JDK API for ResultSet.getRow(), and
> if the author had just written it according to their own javadoc there would
> be no problem.
> See spec here:
> http://java.sun.com/j2se/1.3/docs/api/java/sql/ResultSet.html#getRow()
> The Sun Javadoc does not spell out any exceptions to the required behaviour.
> getRow should always work regardless of whether the result set is scrollable
> because the issue of scrollability is whether the client can *reposition* the
> cursor to change the current row of the result set. Simply *reading* the
> current row number is different and unrelated to changing the current row
> number.
> Therefore getRow() should work for FORWARD_ONLY ResultSets, but Derby
> currently fails on this.
> Quite aside from the spec nonconformance, it's a bit annoying that my
> application has worked fine on Oracle, MS SQL, the JDBC-LDAP bridge driver,
> and even MS Access MDB files via the Sun JDBC-ODBC bridge driver, but then
> the Derby engine falls over just trying to run a simple Select statement on a
> non-updatable forward-only result set - the simplest kind of all!
> I haven't looked at what " theResults.getRowNumber() " does, but I hope the
> fix for this bug is as simple as removing the call to checkScrollCursor;
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