In case you need to migrate your attachments after changing the storage from database to filestore, you can use the following script (use only on OpenERP 7.x):

#!/usr/bin/python

import xmlrpclib

username = 'admin' #the user
pwd = 'password'      #the password of the user
dbname = 'database'    #the database

# Get the uid
sock_common = xmlrpclib.ServerProxy ('<URL>/xmlrpc/common')
uid = sock_common.login(dbname, username, pwd)
sock = xmlrpclib.ServerProxy('<URL>/xmlrpc/object')

def migrate_attachment(att_id):
    # 1. get data
    att = sock.execute(dbname, uid, pwd, 'ir.attachment', 'read', att_id, ['datas'])            

    data = att['datas']

    # Re-Write attachment
    a = sock.execute(dbname, uid, pwd, 'ir.attachment', 'write', [att_id], {'datas': data})

# SELECT attachments:
att_ids = sock.execute(dbname, uid, pwd, 'ir.attachment', 'search', [('store_fname','=',False)])

cnt = len(att_ids)        
i = 0
for id in att_ids:
    att = sock.execute(dbname, uid, pwd, 'ir.attachment', 'read', id, ['datas','parent_id'])

    migrate_attachment(id)
    print 'Migrated ID %d (attachment %d of %d)' % (id,i,cnt)
    i = i + 1

print "done ..."

After running the script, clean up your ir_attachments table:

update ir_attachment set db_datas = null where store_fname is not null
vacuum (full, analyze) ir_attachment

Replace <URL> with your OpenERP installation URL (sorry for that, I do not have enough Karma to post the standard localhost link). Thank you very much to Andreas Brückl for providing the script for OpenERP 6.x (question 711, cannot post the link for same Karma issue).

Please note that in Odoo version, this has changed. The parameter ``ir_attachment.location`` can only take the value ``file`` or ``db``. There's no more ``file:///my/path`` stuff.

It should be noted that an action ``force_storage`` is available on ``ir_attachment`` object and could be easily triggered from python, xmlrpc, or a button to force all the existing attachment to follow the value you have set in ``ir_attachment.location``.

source: https://github.com/odoo/odoo/blob/master/openerp/addons/base/ir/ir_attachment.py#L76

So with this, in odoo, you can switch from file store to db store quite easily.

To be noted also: 'file' is the default value of the parameter ``ir_attachment.location``.

source: https://github.com/odoo/odoo/blob/master/openerp/addons/base/ir/ir_attachment.py#L70

lThank You Giulio Marcon, your script helped me do migrate my attachment files from database OpenERP 7 to file-system.  I only had to change the line

data = att['datas']

With

data = att[0]['datas']

in order to get rid of the message " 'int' object is not iterable "

Attachments are store in ir_attachment table as binary data.

after a few research i found the original files are stored in file system in my ubuntu 18 is 

home->.local->share->odoo->filestore->your_db_name->the first 2 character of the offset of your attachment folder->here you can find the file uploaded by you. 

You have two options for store attachment. Database: irattachment table Folder: ../server/filestore/databasename/

Stored in a folder of your operating system is more efficient. You can see it in Storage configuration

Moisés López - Vauxoo

I see this bug was reported for Windows. We have it with Linux as well - all file types and sizes

If Knowledge Management module is installed, attachments will be stored only in the file system.. No option to store in DB
 

Thank you for the script.

When I try to extract all the documents stored in the database to the file system via XMLRPC, I notice a huge memory usage.

Is there's a way to limit the memory used ?

Thank you.

Version 6 had the option to save attachments onto the file system.

Unfortunately this functionality has been removed from v7 and currently the only option, as Francesco says above, stores them as binary data in the ir_attachment table.

This is a bad feature!

Edit: Sorry, it is correct, this is a comment a not an answer