On Mon, Dec 21, 2009 at 13:34, Sergiu Dumitriu <sergiu(a)xwiki.com> 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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--
Thomas Mortagne