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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4653) Avoid unnecessary round-trip for commit in the client driver
Date Wed, 23 Jun 2010 11:35:50 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4653?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12881648#action_12881648
] 

Kristian Waagan commented on DERBY-4653:
----------------------------------------

Thanks Kathey and Lily.

I committed the follow-up patch with revision 957164.
Since Connection.setAutoCommit(boolean) may theoretically issue a commit, I moved it up before
the call to fetch the transaction id.

> Avoid unnecessary round-trip for commit  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,
DERBY-4653-7_withflowcommittest.diff, DERBY-4653-7_withflowcommittest_comment_update_diff.txt,
DERBY-4653-7_withflowcommittest_comment_update_diff.txt, DERBY-4653-7_withflowcommittest_comment_update_diff_followup.txt,
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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