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From "Lily Wei (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-4653) Avoid unnecessary round-trip for commit/rollback in the client driver
Date Wed, 16 Jun 2010 05:42:24 GMT

     [ https://issues.apache.org/jira/browse/DERBY-4653?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lily Wei updated DERBY-4653:
----------------------------

    Attachment: ReproTransInProgressAttempt.java

Thanks to Kathey. I got to know more in turn of why Connection.close() after Connection.flowrollback()
will cause error "Cannot close a connection while a transaction is still active" for StatementPoolingTest.
As the ReproTransInProgressAttempt.java shows, if we have commit between we are in ResultSet,
we should not flowrollback. If flowrollback remains unchanged, it will detect the state of
the statement and resultSet and keep all the flag as inUnitOfWork etc in the right place and
Connection.close() will not run into error as "Cannot close a connection while a transaction
is still active". 
Due to this reason, I am leading toward to not fix flowrollback() to save round trip and just
keep the change for flowcommit() to improve performance.

> 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: 10.7.0.0
>            Reporter: Kristian Waagan
>            Assignee: Lily Wei
>            Priority: Minor
>         Attachments: _sds_0, DERBY-4653-1.diff, DERBY-4653-2.diff, DERBY-4653-3_withrollback.diff,
DERBY-4653-4_withcommitrollbacktest.diff, DERBY-4653-5_withflowcommitrollback.diff, DERBY-4653-6_withflowcommitrollback.diff,
ReproTransInProgressAttempt.java, SaveRoundClientDS.java, SaveRoundClientDS.java
>
>
> 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 mode.
>         // 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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