diff --git a/openerp/addons/base/ir/ir_attachment.py b/openerp/addons/base/ir/ir_attachment.py
index c636463be10..d3ecfd1b2c7 100644
--- a/openerp/addons/base/ir/ir_attachment.py
+++ b/openerp/addons/base/ir/ir_attachment.py
@@ -138,9 +138,9 @@ class ir_attachment(osv.osv):
         return fname
 
     def _file_delete(self, cr, uid, fname):
-        count = self.search(cr, 1, [('store_fname','=',fname)], count=True)
+        count = self.search_count(cr, 1, [('store_fname','=',fname)])
         full_path = self._full_path(cr, uid, fname)
-        if count <= 1 and os.path.exists(full_path):
+        if not count and os.path.exists(full_path):
             try:
                 os.unlink(full_path)
             except OSError:
@@ -170,14 +170,18 @@ class ir_attachment(osv.osv):
         location = self._storage(cr, uid, context)
         file_size = len(value.decode('base64'))
         attach = self.browse(cr, uid, id, context=context)
-        if attach.store_fname:
-            self._file_delete(cr, uid, attach.store_fname)
+        fname_to_delete = attach.store_fname
         if location != 'db':
             fname = self._file_write(cr, uid, value)
             # SUPERUSER_ID as probably don't have write access, trigger during create
             super(ir_attachment, self).write(cr, SUPERUSER_ID, [id], {'store_fname': fname, 'file_size': file_size, 'db_datas': False}, context=context)
         else:
             super(ir_attachment, self).write(cr, SUPERUSER_ID, [id], {'db_datas': value, 'file_size': file_size, 'store_fname': False}, context=context)
+
+        # After de-referencing the file in the database, check whether we need
+        # to garbage-collect it on the filesystem
+        if fname_to_delete:
+            self._file_delete(cr, uid, fname_to_delete)
         return True
 
     _name = 'ir.attachment'
@@ -315,10 +319,19 @@ class ir_attachment(osv.osv):
         if isinstance(ids, (int, long)):
             ids = [ids]
         self.check(cr, uid, ids, 'unlink', context=context)
-        for attach in self.browse(cr, uid, ids, context=context):
-            if attach.store_fname:
-                self._file_delete(cr, uid, attach.store_fname)
-        return super(ir_attachment, self).unlink(cr, uid, ids, context)
+
+        # First delete in the database, *then* in the filesystem if the
+        # database allowed it. Helps avoid errors when concurrent transactions
+        # are deleting the same file, and some of the transactions are
+        # rolled back by PostgreSQL (due to concurrent updates detection).
+        to_delete = [a.store_fname
+                        for a in self.browse(cr, uid, ids, context=context)
+                            if a.store_fname]
+        res = super(ir_attachment, self).unlink(cr, uid, ids, context)
+        for file_path in to_delete:
+            self._file_delete(cr, uid, file_path)
+
+        return res
 
     def create(self, cr, uid, values, context=None):
         self.check(cr, uid, [], mode='write', context=context, values=values)