[ZODB-Dev] blobs for noobs

[Shane Hathaway]

James Bergstra wrote:
> I'm surprised by the complete silence... was this post sent to the
> wrong list?  What would be a better one?

This is the right list.  I don't know why you didn't get an answer earlier.

>> Where can I find information on using BLOBs outside of plone?  I use
>> ZODB directly from my python programs and I would like to store large
>> files across ZEO.  I'm using a recent ZODB (3.9.3)
>>
>> - I use runzeo.py to start my server, how do I tell it where on the
>> filesystem to put blob data?

Create a ZConfig file that specifies the blob-dir option.  Does anyone 
know where to find documentation of the ZConfig format?  I always cobble 
something together using component.xml and examples.

>> - when using blobs across ZEO, where is the blob data stored on the
>> client side?  Memory? /tmp? cwd?

The blob data is stored in the filesystem directory specified by the 
blob-dir option.  The layout of the directory is normally 8+ levels 
deep, so don't worry about putting too many files in any particular 
subdirectory.

>> - I'm assuming that BLOBs should be manipulated like any other
>> persistent object. How true is this?  What exceptions are there?  How
>> is blob data cached in the client, specifically is it ever
>> automatically flushed? I want to use my BLOB data (read only) after
>> closing the db connection.
>>
>> - where in plone or elsewhere might I find code that would illustrate
>> how blobs should be used?

The BLOB tests provide good documentation of how to use them:

http://svn.zope.org/ZODB/trunk/src/ZODB/tests/blob_basic.txt?rev=103153&view=auto

I hope that test file answers your questions.

Shane