Attachments not persisted when uploaded by xmlrpc or using Document.addAttachment.

== Problem ==

When uploading/storing pages with attachments via XMLRPC API,
existing attachments from existing pages got lost.
This effect seems to occur randomly but can be reproduced 100%.

This is pretty bad, cause nobody expects data lost and will stop us
from using XWiki in production :-/

The attachments are deleted from the database and will produce exceptions
later on. Typical error when trying to touch the attachment:

{{
2010-08-10 18:30:57,494 [http://localhost:8080/xwiki/bin/delattachment/Sandbox/Ant/mediawikioriginal.txt?xredirect=%2Fxw
iki%2Fbin%2Fview%2FSandbox%2FAnt%23Attachments&ajax=1] WARN doc.XWikiAttachment - Failed to load content fo
r attachment [mediawikioriginal.txt@Sandbox.Ant]. This attachment is broken, please consider re-uploading it. Internal e
rror: Error number 3231 in 3: Exception while loading attachment mediawikioriginal.txt of document Sandbox.Ant
Wrapped Exception: No row with the given identifier exists: com.xpn.xwiki.doc.XWikiAttachmentContent#-163312232

2010-08-10 18:30:57,494 [http://localhost:8080/xwiki/bin/delattachment/Sandbox/Ant/mediawikioriginal.txt?xredirect=%2Fxw
iki%2Fbin%2Fview%2FSandbox%2FAnt%23Attachments&ajax=1] WARN .XWikiHibernateAttachmentStore - Error loading attachment
content when deleting attachment mediawikioriginal.txt of doc Sandbox.Ant
}}

== Test "Attachments Got Lost" ==
There is a sample class which you can use to reproduce the problem.
This test uses the XMLRPC-API and stores pages on a XWiki instance.
It also attaches one image to each page.
This test will run ~250 times and thus stores ~250 pages
with ~250 images. Each image will approximately use 40kBytes within the database.
Thus the whole database should grow +10MBytes (250*40kB)
*But when you look into the newly created pages, the attachments are lost!*
No Exception is thrown no error printed - just lost!

== Installation/Setup ==

=== Prepare a separate XWiki for this Test ===
1. Download and unzip "xwiki-enterprise-jetty-hsqldb-2.4.zip"
1. Start this preconfigured XWiki (start_xwiki.bat)

=== Prepare the Test-Runner ===
1. Create a new Java Project within your favorite Eclipse workspace
1. Copy ##MassiveUploadSimulation.java## into the source folder
1. Download the following JARs (see http://platform.xwiki.org/xwiki/bin/view/Features/XMLRPCJavaExamples)
1*. commons-logging-1.1.1.jar
1*. swizzle-confluence-1.2-20080419-xwiki.jar
1*. ws-commons-util-1.0.2.jar
1*. xmlrpc-client-3.1.jar
1*. xmlrpc-common-3.1.jar
1*. xwiki-core-2.4.jar
1*. xwiki-core-xml-2.4.jar
1*. xwiki-core-xmlrpc-client-2.4.jar
1*. xwiki-core-xmlrpc-model-2.4.jar
1. Copy the JARs into the project
1. Register the JARs to your CLASSPATH

=== Run the Test-Runner ===

1. Run ##MassiveUploadSimulation## as regular 'Java Application'

warning}}Don't run this simulation on your productive XWiki installation!{{/warning

=== Test It ===
To see what's wrong, just pick up your browser and open a random page (ex. Page67) and watch for the embedded image. It's lost!