Bug: UpdateAttachmentDoesntUpdate

The old version stays.

Test case

I uploaded an excel spreadsheet without checking link or the other checkbox. Then I checked that it was OK. Then I closed the downloaded spreadsheet in excel, edited the original file on the disk and closed it again. Then I pressed action and uploaded the new version without changing the comments or checkboxes. Then I checked the uploaded version but it hadn't changed.

Environment

-- TWikiGuest - 12 Apr 2002

Follow up

Did you flush your document cache in IE? Maybe you were looking at the old spreadsheet from the cache, and the new spreadsheet is correctly uploaded to the server.

-- JohnRouillard - 12 Apr 2002

This is similar to ViewAfterSaveCachesOldPage, but for attachments instead of topics. As John points out, it's most likely a caching issue. As with that bug, we could probably fix this through BrowserAndProxyCacheControl, avoiding confusion when you have just uploaded an updated file.

However, it's a bit harder in the attachment case, since TWiki is not involved in the attachment download - either we would have to get TWiki to serve all attachments (a big change, and a performance hit), or we'd need to tell the webserver to send out special HTTP headers to limit caching for attachments (ideally, the fact that an attachment had been uploaded would prevent caching - but that's hard to do without Apache's ModPerl IMO).

The web caching community generally says that the only way to ensure that an updated file is not cached is to give it a new URL - this could be done by involving TWiki in downloads (suffixing a unique string to the URL, as with RefreshEditPage), or by putting the new attachment in a different file (wasting space where RCS can handle the file efficiently).

Overall, the simplest way to get control over attachment caching is to add this into TWiki, but that's quite a big step to take.

-- RichardDonkin - 20 Apr 2002

Fix record