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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-4653) Avoid unnecessary round-trip for commit/rollback in the client driver
Date Wed, 12 May 2010 08:14:52 GMT
Avoid unnecessary round-trip for commit/rollback in the client driver

                 Key: DERBY-4653
                 URL: https://issues.apache.org/jira/browse/DERBY-4653
             Project: Derby
          Issue Type: Improvement
          Components: JDBC, Network Client
    Affects Versions:
            Reporter: Kristian Waagan
            Priority: Minor

The methods Connection.commit() and Connection.rollback() in the client driver cause a round-trip
to the server even if the commit/rollback is unnecessary (i.e. there is nothing to commit
or roll back).
Comments suggest (see below) that this can be optimized, such that the commands are flowed
to the server only when required. It can be seen that this optimization has been used other
places in the client driver. Never the less, it must be checked that this optimization doesn't
have side-effects.

This issue came up in connection with connection pooling, where a pool implementation always
issued a rollback to make sure there was no active transaction on the connection handed out.

>From Connection.flowCommit:
        // Per JDBC specification (see javadoc for Connection.commit()):
        //   "This method should be used only when auto-commit mode has been disabled."
        // However, some applications do this anyway, it is harmless, so
        // if they ask to commit, we could go ahead and flow a commit.
        // But note that rollback() is less harmless, rollback() shouldn't be used in auto-commit
        // This behavior is subject to further review.

        //   if (!this.inUnitOfWork)
        //     return;
        // We won't try to be "too smart", if the user requests a commit, we'll flow a commit,
        // regardless of whether or not we're in a unit of work or in auto-commit mode.

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