On Mon, Dec 21, 2009 at 13:34, Sergiu Dumitriu <[email protected]> wrote:
> Hi devs,
>
> Currently the getDocument method always goes to the storage to retrieve
> the document, even if the same document has just been retrieved. This
Note to be more clear: in public API only not private one (because the
XWikiDocument is got from cache storage and not reloaded each time
from the database). And the exact issue is that the XWikiDocument is
cloned in the Document instance so when you ask again for the Document
you don't get the same instance of XWikiDocument behind the scene.
> means that the following code will not work:
>
> #set($d = $xwiki.getDocument('X'))
> $d.setTitle('the title')
> $xwiki.getDocument('X').getTitle() # will not print 'the title'
>
> I'd like to change getDocument so that it first searches in a map of
> used documents in the current context. This means the following:
> - getDocument searches in XWikiContext.usedDocuments (or better, in the
> ExecutionContext)
Well Document class is old API so not sure it's if really better in
ExecutionContext
> - if found, return the value from there
> - if not, go to the storage, return it to the caller
> - when the document is changed for the first time, i.e. when
> api.Document.getDoc() is called, clone the original document and put it
> in usedDocuments
> - as a special case, PreviewAction also puts the updated context
> document in usedDocuments
>
> This means that consecutive calls for retrieving a (changed) document
> will always return the same object. This prevents possible preview bugs,
> like http://jira.xwiki.org/jira/browse/XABLOG-14 or
> http://jira.xwiki.org/jira/browse/XWIKI-4689
>
> Yet this is an important behavior change. Do you think anybody is using
> this "feature", and actually expects the above code example to work as
> it does now?
>
> Also, we must be careful with the performance, since this new map could
> get big, holding all the documents in the database. Perhaps a LRU
> fixed-size map would be better, although this breaks the uniqueness
> guarantee.
>
> So, WDYT?
>
> 1. Should we introduce this cache?
+1 for a context cache for public Document instances, makes the
scripts more natural
> 2. Should it be limited in size?
Always better I think
>
> --
> Sergiu Dumitriu
> http://purl.org/net/sergiu/
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> http://lists.xwiki.org/mailman/listinfo/devs
>
--
Thomas Mortagne
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