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Date: Thu, 7 Jun 2007 22:06:25 -0700 (PDT)
From: "Myrna van Lunteren (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Updated: (DERBY-2762) Document, verify and fix
 synchronization issues related to Clob in the embedded driver
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     [ https://issues.apache.org/jira/browse/DERBY-2762?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Myrna van Lunteren updated DERBY-2762:
--------------------------------------

    Fix Version/s:     (was: 10.3.0.0)

Removing 10.3 fixin, I don't think this is a must for 10.3 If it implemented in time fixin can be set when the issue gets marked resolved.

> Document, verify and fix synchronization issues related to Clob in the embedded driver
> --------------------------------------------------------------------------------------
>
>                 Key: DERBY-2762
>                 URL: https://issues.apache.org/jira/browse/DERBY-2762
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC
>    Affects Versions: 10.3.0.0
>            Reporter: Kristian Waagan
>
> Synchronization with respect to Clobs is a bit tricky.
> A full review of synchronization should be performed, and documentation and actual behavior must be made in agreement with each other.
> The synchronization wrt. Clob is made tricker due to the many streams that can be used to read or write its value.
> The main classes to review will be (there might be more):
>  a) EmbedClob
>  b) StoreStreamClob
>  c) ClobStreamControl (may be renamed to TemporaryClob)
>  d) ClobUtf8Writer
>  e) ClobAsciiStream
>  f) ClobUpdateableReader
> We should also clarify and document what is supposed to be allowed. Can
> you read from one stream and write to another one at the same time, both
> from the same Clob?
> Can you expect the ascii stream and the character stream to be in sync
> if you read from both of them?
> A related issue is that of garbage collection of underlying resources
> before the streams are closed. DERBY-2734 has already been filed for
> this.
> I would like to try a little experiment by using a few simple
> annotations to document intended synchronization policies. These are the
> annotations defined in the book "Java Concurrency in Practice" by Brian
> Goetz et al, and the JavaDoc for them can be found here: 
> http://javaconcurrencyinpractice.com/annotations/doc/index.html
> Since we are still using Java 1.4, the annotations must be used as
> comments. I still think they are valuable, as we do not use any tools to
> document/check synchronization anyway.
> Briefly, the following four annotations are defined:
>  @GuardedBy
>  @Immutable
>  @NotThreadSafe
>  @ThreadSafe

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