[ http://issues.apache.org/jira/browse/DERBY-210?page=all ]
Deepa Remesh updated DERBY-210:
-------------------------------
Attachment: derby-210-patch4-v2.diff
derby-210-patch4-v2.status
Attaching a patch 'derby-210-patch4-v2.diff' which fixes the finalization code
in Statement classes in client driver. This patch is in preparation for the
fixes to memory leaks.
Summary of changes:
* Changes the finalizers in Statement classes to do only client-side cleanup.
No network operations are done in the finalizers.
* Adds markClosed method to PreparedStatement class which overrides the
markClosed method in Statement class. All client-side cleanup code is moved to
markClosed method. Two forms of markClosed method are added:
- markClosed() method will perform clean up but will not remove Statement
from the open statements list and PreparedStatement from the commit and
rollback listeners list in org.apache.derby.client.am.Connection. This method
is called from finalize(), Connection#markStatementsClosed(), and to close
positioned update statements. For the finaizer to be called, the Statement
should not have any references and so it should have been already removed from
the lists. Connection#markStatementsClosed method explicitly removes the
Statement from open statements list. Positioned update statements are not added
to the open statements list. Hence, markClosed() is called in these cases.
- markClosed(true) will additionally remove the statement objects from the
lists. This is called from close() method.
* After these changes, it is not required to override close(), closeX() and
finalize() methods in PreparedStatement class since they contain same code as
in Statement class. So these methods are removed.
With these changes, I ran derbynetclientmats with Sun JDK 1.4.2.
jdbcapi/dbMetaDataJdbc30.java failed. This test has been already fixed by
David.
Please take a look at this patch. Thanks.
> 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-v2.diff, derby-210-patch4-v2.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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