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From "Kathey Marsden (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-210) Network Server will leak prepared statements if not explicitly closed by the user until the connection is closed
Date Sun, 19 Feb 2006 06:11:26 GMT
    [ http://issues.apache.org/jira/browse/DERBY-210?page=comments#action_12366955 ] 

Kathey Marsden commented on DERBY-210:
--------------------------------------

Thank you Deepa for the explanations.     I think I finally have my head around this change.
 I think there actually is a problem with not sending CLSQRY for finalize.  If I  have 20,000
open valid and referenced  prepared statements and then I dereference them, I will continue
to have 20,000 open statements on the server until the connection ends.  Those statements
will get reused if I prepare more statements,  but will never actually get cleaned up until
the connection ends.

The reason for the change was to take the autocommit out of finalize and with that I fully
agree, but I wonder: why do  we have to take out the CLSQRY?  writeCloseResultSets takes a
boolean allowAutocommits.  Could we continue to call it for finalize but just with that parameter
set to false?

Also I would appreciate input from others on this.  Sorry Deepa to string this along so long.


> 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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