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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 Tue, 21 Feb 2006 17:52:18 GMT
    [ http://issues.apache.org/jira/browse/DERBY-210?page=comments#action_12367235 ] 

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

There was a separate thread on this issue on the list  where  concerns were voiced about doing
the result set cleanup work in finalize and maybe creating another thread to do that.  

I talked with Deepa a bit on IRC about the impact of submitting her patch as is without the
result set cleanup.
The summary is.  

Before Deepa's patch 4:
- No statements or result sets get cleaned up until the end of the connection unless explicitly
closed

After Deepa's patch 4:
- No statements or result sets get cleaned up until the end of the connection unless explicitly
closed.

After Deepa's planned patch 5:
Most statements and result sets get cleaned up automatically.


So, I am of the opinion that Deepa's patch can go in as is and another  Jira entry filed for
the result set cleanup.  Her planned work  is a huge improvement over the current state. 
She does not need to include the result set cleanup in her patch for DERBY-210



> 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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