Re: [dtp-connect-dev] Reduce the Derby connection reference

[Hui.Cao@xxxxxxxxxx]

Hey Rob,
        Thanks
for your reply! I still think supporting both embeded derby and network
derby is necessary for DTP. The following is an exerpt from the Derby developer's
guide:
Getting a nested connection
When you are executing a method within
SQL, that method might need to reuse the
current connection to the database in
order to execute more SQL statements. Such a
connection is called a nested connection.
The way for a method to get a nested
connection is to issue a connection
request using the connection URL.
jdbc:default:connection
URL attributes are not supported as
part of this connection URL. Any URL attributes
specified in a Properties object, user
name, or password that are passed to a
java.sql.DriverManager.getConnection()
call will be ignored.

I haven't investigated into this problem
thoroughly, but I feel this might be an alternative way to tackle the "single
connection per vm" problem. If we go this way, then I can just compare
the newly created connection with the shared connection to see whether
they are the same and whether I should close it. What do you think? 

Best Regards!

Max ( Hui ) Cao
DTP SQL Dev Tools Committer
Sr S/W Eng - Dev
Sybase, Inc. Shanghai, China

rcernich@xxxxxxxxxx
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02/24/2006 11:15 AM

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Subject	Re: [dtp-connect-dev] Reduce the Derby connection reference

Hey Max,

Managed connections must be closed by calling
IConnectionProfile.disconnect().  The life cycle of the managed connection
is managed through IConnectionProfile.connect() and
IConnectionProfile.disconnect().

The embedded Derby connection is a special beast.  There can only
ever be a
single connection within a VM, which is why this reference counting method
is employed by the connection factory.  That said, the java.sql.Connection
returned by the IConnection object will be the same for all invocations
on
the connection factory for a given embedded Derby connection profile.

If you are getting errors in the DSE because the connection can't be
created, my guess is that a connection to that DB is being created outside
the context of the connection profile's connection factory.  Note,
this is
a limitation of the embedded Derby connection profile.

If this is important to you, I would suggest using Derby in a networked
mode.  Derby behaves more like a "normal" DB when running
as a networked
DB.  See the following mailing list entry along with the Derby
documentation for instructions on setting this up
(http://dev.eclipse.org/mhonarc/lists/dtp-dev/msg00164.html).  (Note,
there
are two different driver definitions for Derby; one for embedded Derby
which is used by the embedded Derby connection profile, and one for
networked Derby which should be used with the generic DB connection
profile.

Please let me know if you need anything else.
Rob

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