[ZODB-Dev] Blobs, Copies, and Exports (Zope 3)

[Christophe Combelles]

Jeff Shell a écrit :
> For the past few years we've been using an ugly, but working, trick to  
> export data out of a Zope 3 instance without exporting every bit of  
> content. Given an object to export, we use  
> 'locationCopy' (zope.location.pickling) to get a deep copy, set the  
> __parent__ attribute of the copied object to None, put it in the ZODB  
> root (root[EXPORT_KEY] = detached_copy), and then commit the  
> transaction. This is so that we have the 'oid' and connection needed  
> for ZODB's 'exportFile' to work.
> 
> If there's a better way of setting `__parent__` to None (or just not  
> following the __parent__ ref during Export, without affecting the  
> saved state in the database), I'd love to know. But that's an aside.
> 
> I exported some content tonight that had Blobs in it. Upon import, I  
> noticed that the blob files in the destination were empty (zero- 
> length). Looking at the ZEXP file, I could see the BLOBSTART markers,  
> but could see no binary data. Tracing down into the export, and then  
> just playing around with 'locationCopy' to make other detached copies,  
> I noticed that the Blob contents were never copied into the new file.
> 
> What can I do here? I'm in the midst of a botched deployment of some  
> content updates for a customer. I thought that copying something  
> 'containing' a Blob would cause its contents to be copied. If this is  
> an exercise for application layer code, how can I get plugged in and  
> know when a Blob is being copied inside of a deep copy?


I suppose it is related to this?
https://bugs.launchpad.net/zope3/+bug/240381


> 
> Thanks,
> 
> --
> Jeff Shell
> jeff at bottlerocket.net
> 
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