Thread: Java Studio Creator Fix/Hack

Hi everyone, I noticed at TODO for getMetaData() on the 8.0 and figured
I'd give this task a try.  I now am able to use Java Studio Creator
with Postgresql 7.4.6.

couldn't access the postgresql sites for the past couple of days so I
posted my hack on the Sun Software Forums.
http://swforum.sun.com/jive/thread.jspa?threadID=50150&tstart=15

here is was I posted:

Ok so I've noticed that there have been a few of us Postgres people
trying to use JSC with our favourite Database. I am posting the fix
here because i can't get access to the Postgresql websites(very odd).

if you check out the postgres jdbc code from their cvs change
org.postgresql.jdbc2.AbstractJdbc2Statement.getMetaData() to the
following.
===========START OF CODE HACK===============

public ResultSetMetaData getMetaData() throws SQLException
{ ResultSet rs = null;
checkClosed();
rs = getResultSet();

if(rs == null)
{
// the following code hack has not been fully tested, therefor use at
your own risk.
/// by Pucky Loucks of How2share Technologies (creators of PiXPO)

StatementResultHandler handler = new StatementResultHandler();

connection.getQueryExecutor().execute(preparedQuery,
preparedParameters,
handler,
0,
0,
QueryExecutor.QUERY_ONESHOT);
rs = handler.getResults().getResultSet();
}

return rs.getMetaData();
}
===================END OF CODE HACK=====
then run ant for pgjdbc and use the postgresql.jar that is in the jar
directory, and volia.

Enjoy.

Pucky Loucks
Senior Systems Architect
How2Share Technologies Inc.

On Fri, 10 Dec 2004, Pucky Loucks wrote:

> Hi everyone, I noticed at TODO for getMetaData() on the 8.0 and figured
> I'd give this task a try.  I now am able to use Java Studio Creator
> with Postgresql 7.4.6.
>
> public ResultSetMetaData getMetaData() throws SQLException
> { ResultSet rs = null;
> checkClosed();
> rs = getResultSet();
>
> if(rs == null)
> {
> // the following code hack has not been fully tested, therefor use at
> your own risk.
> /// by Pucky Loucks of How2share Technologies (creators of PiXPO)
>
> StatementResultHandler handler = new StatementResultHandler();
>
> connection.getQueryExecutor().execute(preparedQuery,
> preparedParameters,
> handler,
> 0,
> 0,
> QueryExecutor.QUERY_ONESHOT);
> rs = handler.getResults().getResultSet();
> }
>
> return rs.getMetaData();
> }
> ===================END OF CODE HACK=====


This patch doesn't really work.  It assumes that the PreparedStatement
doesn't have side effects and that all parameters have been set.

Consider:

PreparedStatement pst = con.prepareStatement("UPDATE tab SET x=x+1");
pst.getMetaData();
pst.execute();

Now all of a sudden x = x+2.  Actually your patch will throw a
NullPointerException, but that's a simple code issue.

Consider:

PreparedStatement pst = con.prepareStatement("SELECT * FROM t WHERE x=?");
pst.getMetaData();

Fails with: org.postgresql.util.PSQLException: No value specified for
parameter 1.

The planned way to implement this feature is with the V3 protocol issuing
Parse/Bind/Describe/ClosePortal without ever executing it.

Kris Jurka

Pucky Loucks wrote:

> org.postgresql.jdbc2.AbstractJdbc2Statement.getMetaData() to the following. [...]

> connection.getQueryExecutor().execute(preparedQuery,
> preparedParameters,
> handler,
> 0,
> 0,
> QueryExecutor.QUERY_ONESHOT);
> rs = handler.getResults().getResultSet();
> }

Danger, danger. This actually *executes* the query.
Statement.getMetaData() isn't meant to do that!

-O

I should have only said HACK not fix... :)   Totally understand that
there is a better way to do it, I just need to get something working,
(this is not for production use) therefore hitting the database is fine
for me right now, and all statements are "select * from tablename"
again this is specific hack for Java Studio Creator.

Can't wait till a real JDBC Developer attacks the problem.

Thanks for the awesome work you guys do!

Pucky Loucks
How2Share Technologies Inc.

On 10-Dec-04, at 5:53 PM, Kris Jurka wrote:I s

>
>
> On Fri, 10 Dec 2004, Pucky Loucks wrote:
>
>> Hi everyone, I noticed at TODO for getMetaData() on the 8.0 and
>> figured
>> I'd give this task a try.  I now am able to use Java Studio Creator
>> with Postgresql 7.4.6.
>>
>> public ResultSetMetaData getMetaData() throws SQLException
>> { ResultSet rs = null;
>> checkClosed();
>> rs = getResultSet();
>>
>> if(rs == null)
>> {
>> // the following code hack has not been fully tested, therefor use at
>> your own risk.
>> /// by Pucky Loucks of How2share Technologies (creators of PiXPO)
>>
>> StatementResultHandler handler = new StatementResultHandler();
>>
>> connection.getQueryExecutor().execute(preparedQuery,
>> preparedParameters,
>> handler,
>> 0,
>> 0,
>> QueryExecutor.QUERY_ONESHOT);
>> rs = handler.getResults().getResultSet();
>> }
>>
>> return rs.getMetaData();
>> }
>> ===================END OF CODE HACK=====
>
>
> This patch doesn't really work.  It assumes that the PreparedStatement
> doesn't have side effects and that all parameters have been set.
>
> Consider:
>
> PreparedStatement pst = con.prepareStatement("UPDATE tab SET x=x+1");
> pst.getMetaData();
> pst.execute();
>
> Now all of a sudden x = x+2.  Actually your patch will throw a
> NullPointerException, but that's a simple code issue.
>
> Consider:
>
> PreparedStatement pst = con.prepareStatement("SELECT * FROM t WHERE
> x=?");
> pst.getMetaData();
>
> Fails with: org.postgresql.util.PSQLException: No value specified for
> parameter 1.
>
> The planned way to implement this feature is with the V3 protocol
> issuing
> Parse/Bind/Describe/ClosePortal without ever executing it.
>
> Kris Jurka
>
> ---------------------------(end of
> broadcast)---------------------------
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>
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