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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-2762) Document, verify and fix synchronization issues related to Clob in the embedded driver
Date Mon, 06 Jul 2009 18:27:15 GMT

     [ https://issues.apache.org/jira/browse/DERBY-2762?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Rick Hillegas updated DERBY-2762:
---------------------------------

       Urgency: Normal
    Issue Type: Task  (was: Bug)

Triaged for 10.5.2: Assigned normal urgency. Changed from Bug to Task because this is a request
for analysis--it's likely that that analysis will result in the logging of bugs.

> 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: Task
>          Components: JDBC
>    Affects Versions: 10.3.1.4
>            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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