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From Kristian Waagan <kristian.waa...@oracle.com>
Subject Re: Table exists in same JVM after Derby is shutdown
Date Tue, 09 Aug 2011 05:43:00 GMT
On 08.08.11 16:41, Pavel Bortnovskiy wrote:
> Thank you, Dag.
>
> It looks like in order to get this to work, I had to make two calls to
> DriverManager.getConnection.
> Combining "/shutdown=true;drop=true/" didn't work.
> So, is this the correct implementation (if in-line image doesn't work,
> please see attachment):

Hello Pavel,

To simply drop an in-memory database, you only need the drop attribute. 
Shutdown of the specified database happens as part of the drop operation.

It is correct that you need two calls to DriverManager.getConnection if 
you want to drop a database and additionally shut down the Derby engine. 
For clarity, note that there is a difference between shutting down a 
specific database and the Derby engine/system.

Further, shutting down an in-memory database does not drop it, neither 
does shutting down the Derby engine. I don't know, maybe it would make 
sense to drop all in-memory databases when the Derby system is shut down 
- but that's not being done currently.


Hope this helps,
-- 
Kristian

>
>
>
>
>
> From: 	dag.wanvik@oracle.com (Dag H. Wanvik)
> To: 	"Derby Discussion" <derby-user@db.apache.org>
> Date: 	08/05/2011 06:36 PM
> Subject: 	Re: Table exists in same JVM after Derby is shutdown
>
>
> ------------------------------------------------------------------------
>
>
>
> Pavel Bortnovskiy <PBortnovskiy@Jefferies.com> writes:
>
>  > 1) I create an in-memory database and then a table in it.
>  > Then the database is shut down.
>  > I would expect that the shutdown effectively cleans everything up.
>  > Is it not so?
>
> Ah, I misunderstood you Pavel. Have a look here:
>
> http://wiki.apache.org/db-derby/InMemoryBackEndPrimer
>
> As you can see, you need to provide the "drop=true" connection
> attribute to wipe the data.
>
> Thanks,
> Dag
>
>  >
>  > Thanks,
>  > Pavel.
>  >
>  >
>  >
>  > From:
>  > dag.wanvik@oracle.com (Dag H. Wanvik)
>  > To:
>  > "Derby Discussion" <derby-user@db.apache.org>
>  > Date:
>  > 08/05/2011 05:57 PM
>  > Subject:
>  > Re: Table exists in same JVM after Derby is shutdown
>  >
>  >
>  >
>  > Pavel Bortnovskiy <PBortnovskiy@Jefferies.com> writes:
>  >
>  >> Hello, all:
>  >>
>  >> While executing a bunch of JUnit tests within the same JVM (all
> executed
>  >
>  >> by IntelliJ IDEA) I started seeing strange and unexpected errors
>  > occurring
>  >> .
>  >> Upon closer inspection, I noticed that in many of those tests tables
>  > with
>  >> the same names are attempted to be created.
>  >> Then I realized that although Derby is shutdown and then re-created,
> the
>  >
>  >> tables remain, thus causing collisions.
>  >
>  > The "create=true" connection attribute is ignored (with a warning) if
>  > the database with the same name alrady exists.
>  >
>  >>
>  >> I've created a digest (attached) which is executed as one JUnit test to
>  >> illustrate what I'm seeing.
>  >> The behavior I would expect is that once Derby is shutdown, no tables
>  >> would remain in the JVM, and if a database (with the same name) is
>  >> re-created, it would be a tabula rasa.
>  >
>  > The tables are no longer in memory (or should not be unless you found a
>  > bug), but they are not erased from the disk image of the database. As
>  > per the above, one would need to explicitly delete it using OS file
>  > system tools for the data to be cleared. Some JUnit tests delete tables
>  > in TestCase#tearDown, others use singleUseDatabaseDecorator to isolate
>  > itself from the rest of the tests. The tests not necessarily very
>  > consistent in their patterns for this..
>  >
>  > Dag
>  >
>  >>
>  >> Can you please let me know whether my expectations are erroneous and
>  >> whether I should find workarounds (albeit trivial to implement).
>  >> However, what would concern me in that case is that the tables and the
>  >> data remain in the JVM, thus consuming memory
>  >> (and, if unused, creating memory leaks).
>  >>
>  >> Thank you,
>  >>
>  >> Pavel.
>  >>

< snip >

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