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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-3581) Changing certain properties on client DataSource objects causes existing connections to reflect the new values
Date Sun, 30 Mar 2008 13:21:24 GMT
Changing certain properties on client DataSource objects causes existing connections to reflect
the new values
--------------------------------------------------------------------------------------------------------------

                 Key: DERBY-3581
                 URL: https://issues.apache.org/jira/browse/DERBY-3581
             Project: Derby
          Issue Type: Bug
          Components: JDBC, Network Client
    Affects Versions: 10.3.2.1, 10.4.0.0, 10.5.0.0
            Reporter: Kristian Waagan


The client driver has code propagating changes made to the DataSource to existing connections
created by that DataSource.
There is some discussion of this in the thread http://www.nabble.com/ConnectionPoolDataSource-properties-td15740457.html,
and there is also an example of what can happen due to this "feature".

Besides from being a bug with the potential to cause strange errors in deployment, the issue
also makes the client driver code harder to read and understand.
As far as I can see, there is also some related code in other parts of the client driver,
for instance for "fully" resetting statements. There is mention of dynamic versus static sections
in the comments (this one from am.Statement):

    // If a dataSource is passed into resetClientConnection(), then we will assume
    // properties on the dataSource may have changed, and we will need to go through
    // the open-statement list on the connection and do a full reset on all statements,
    // including preparedStatement's and callableStatement's.  This is because property
    // change may influence the section we allocate for the preparedStatement, and
    // also the cursor attributes, i.e. setCursorSensitivity().
    // If no dataSource is passed into resetClientConnection(), then we will do the
    // minimum reset required for preparedStatement's and callableStatement's.

Note that the reset code for statements is also invoked when ClientPooledConnection.getConnection()
is invoked. I do not understand why we should reset statements when we get a new logical connection.

Further, I also suspect the concept of a deferred reset has been introduced because of the
feature/bug described by this Jira issue. A deferred reset seems to be a mechanism to avoid
a round-trip to validate the newly changed DataSource properties (typically user, password
and security mechanism).
I will look into removing code related to deferred resets as well. If you have historic information
about these parts of the driver, I would appreciate if you share it with the community if
possible.

Just to be clear, it is my opinion that changed DataSource properties should take effect when
one of the following methods is invoked:
 * DataSource.getConnection()
 * ConnectionPoolDataSource.getPooledConnection()
 * XADataSource.getXAConnection()

All of the methods above returns a physical connection. Properties like user name and password
are associated with the physical connection, and thus requests to obtain a logical connection
should not cause any of these properties to change.

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