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From "Knut Anders Hatlen (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-557) Client driver gets OutOfMemoryError when re-executing statement without closing ResultSet
Date Fri, 16 Sep 2005 14:43:56 GMT
    [ http://issues.apache.org/jira/browse/DERBY-557?page=comments#action_12329549 ] 

Knut Anders Hatlen commented on DERBY-557:
------------------------------------------

Kathey,

Thanks for committing. Answers to your questions follow.

1) I could write a test like "run this loop for x minutes and see if an OutOfMemoryError is
thrown". With a small heap it would run out of memory fairly soon. Is this the kind of test
you want? Where does such a test belong? derbylang? derby*mats?

2) I merged the changes and tested with 10.1 earlier today. Didn't get OutOfMemoryError and
derbyall ran successfully (except some encryption tests, as usual). Merge command: svn merge
-r 289538:289539 trunk-directory 10.1-directory

> Client driver gets OutOfMemoryError when re-executing statement without closing ResultSet
> -----------------------------------------------------------------------------------------
>
>          Key: DERBY-557
>          URL: http://issues.apache.org/jira/browse/DERBY-557
>      Project: Derby
>         Type: Bug
>   Components: Network Client
>     Versions: 10.1.1.0, 10.1.2.0, 10.2.0.0
>     Reporter: Knut Anders Hatlen
>     Assignee: Knut Anders Hatlen
>     Priority: Minor
>      Fix For: 10.1.2.0, 10.2.0.0
>  Attachments: DERBY-557.diff, DERBY-557.stat, derbyall_report.txt
>
> When re-executing a statement without closing the old ResultSet, some of the old ResultSet's
resources are not released, and the network client will eventually get an OutOfMemoryError.
> Example:
> 	Connection c = DriverManager.getConnection("jdbc:derby://localhost/mydb");
> 	PreparedStatement ps = c.prepareStatement("select * from sys.systables");
> 	while (true) {
> 		ResultSet rs = ps.executeQuery();
> 	}
> This code will run for some time and then throw an OutOfMemoryError. Same thing happens
with Statement instead of PreparedStatement. If rs.close() is added in the loop, the code
works. Explicitly closing the ResultSet should not be necessary according to this quote from
the JDBC 3.0 spec:
>   For Select statements, the statement is complete when the associated result set is
closed. The result set is closed as soon as one of the following occurs:
>      - all of the rows have been retrieved
>      - the associated Statement object is re-executed
>      - another Statement object is executed on the same connection

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