[ http://issues.apache.org/jira/browse/DERBY-210?page=all ]
Deepa Remesh updated DERBY-210:
-------------------------------
Attachment: derby-210-patch4.diff
derby-210-patch4.status
Attaching 'derby-210-patch4.diff' which changes the finalizer method in
Statement and PreparedStatement classes in the client driver. Changes are:
1. In PreparedStatement class, the finalizer was calling closeX method, which
was doing:
* Call super.closeX() ---> Statement.closeX()
* Cleanup parameter objects - parameterMetaData_, sql_, parameters_ array
* Remove the PreparedStatement from connection_.CommitAndRollbackListeners_
list
Changes done by patch:
* Add a new method markClosed() which will free client-side resources.
* The new method is named markClosed() to keep it uniform with naming
convention in superclass.
* This method is called from close() and finalize() methods.
* markClosed() method will call super.markClosed() to perform cleanup of
parent class. It will cleanup the objects specific to PreparedStatement, which
are ParameterMetaData and parameters. It also removes the PreparedStatement
form the list in Connection object.
2. In Statement class, the finalizer was calling closeX method, which was doing:
* Close any open cursors for this statement on the server.
- If result set is open on server, send CLSQRY to the server.
- check if autocommit is required when closing result sets and flow
a commit to server, if required
* Call Statement.markClosed(), which does
- Mark close the result sets on the client
- If cursor name was set on the statement, remove it from
Connection.clientCursorNameCache_
- Call markClosed() on prepared statements for auto generated keys
- Call markClosedOnServer(), which frees up the section. The freed
section will be re-used by new statements.
* Remove the Statement from Connection.openStatements_ list
* Cleanup ResultSetMetaData
Changes done by patch:
* Move the cleanup of ResultSetMetaData and remove of Statement from
Connection.openStatements_ list into markClosed() method. This will keep all
client-side cleanup in markClosed().
* Change the finalizer to just call markClosed(). This method frees up
client-side resources and operates on synchronized collections. So I have
removed the synchronize block from the finalizer.
* The autocommit logic does not exist in the finalizer since only
markClosed() is called from finalizer. This will avoid untimely commits which
was causing the regression in the test lang/updatableResultSet.java
With this patch, I ran derbynetclientmats with Sun JDK1.4.2 on Windows XP.
Just before submitting this, I was re-reading the patch and noticed there is no
need to override close and closeX method in PreparedStatement since these
methods are doing exactly same things as the methods in Statement class.
close() method in both classes just call closeX. And closeX does server-side
cleanup and calls markClosed. And markClosed in PreparedStatement calls the
super.markClosed. So there is no need for a close() and closeX() in
PreparedStatement. This is possible because of the name change suggested by
Bryan. Thanks again. I hope this change is okay. I will re-run
derbynetclientmats and will submit a revised patch4.
Bryan, if you get time, I would appreciate if you can look at this patch and
let me know if it covers your comments.
> Network Server will leak prepared statements if not explicitly closed by the
> user until the connection is closed
> ----------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-210
> URL: http://issues.apache.org/jira/browse/DERBY-210
> Project: Derby
> Type: Bug
> Components: Network Client
> Reporter: Kathey Marsden
> Assignee: Deepa Remesh
> Attachments: DOTS_ATCJ2_Derby-noPatch.png, DOTS_ATCJ2_Derby-withPatch.png,
> derby-210-patch1.diff, derby-210-patch2.diff, derby-210-patch2.status,
> derby-210-patch3.diff, derby-210-patch4.diff, derby-210-patch4.status,
> derby-210-v2-draft.diff, derby-210-v2-draft.status, derbyStress.java
>
> Network server will not garbage collect prepared statements that are not
> explicitly closed by the user. So a loop like this will leak.
> ...
> PreparedStatement ps;
> for (int i = 0 ; i < numPs; i++)
> {
> ps = conn.prepareStatement(selTabSql);
> rs =ps.executeQuery();
> while (rs.next())
> {
> rs.getString(1);
> }
> rs.close();
> // I'm a sloppy java programmer
> //ps.close();
> }
>
> To reproduce run the attached program
> java derbyStress
> Both client and server will grow until the connection is closed.
>
> It is likely that the fix for this will have to be in the client. The client
> does not send protocol to close the prepared statement, but rather reuses the
> PKGNAMCSN on the PRPSQLSTT request once the prepared statement has been
> closed. This is how the server knows to close the old statement and create a
> new one.
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