Memory erron in openerp 6.1 - odoo

Question

When physical inventory is been set to make the stock moves to zero value, it runs for a long time and throws an error like memory error.
Nearly 2000 products are in stock location we need to make the real stock zero.
ERROR:
File "/home/administrator/workspace/server/openerp/osv/osv.py", line 121, in wrapper
return f(self, dbname, *args, **kwargs)
File "/home/administrator/workspace/server/openerp/osv/osv.py", line 176, in execute
res = self.execute_cr(cr, uid, obj, method, *args, **kw)
File "/home/administrator/workspace/server/openerp/osv/osv.py", line 164, in execute_cr
return getattr(object, method)(cr, uid, *args, **kw)
File "/home/administrator/workspace/addons/stock/stock.py", line 2665, in action_done
move_obj.action_done(cr, uid, inventory_move_ids, context=context)
File "/home/administrator/workspace/addons/stock/stock.py", line 2253, in action_done
self._create_product_valuation_moves(cr, uid, move, context=context)
File "/home/administrator/workspace/addons/stock/stock.py", line 2187, in _create_product_valuation_moves
if move.product_id.valuation == 'real_time': # FIXME: product valuation should perhaps be a property?
File "/home/administrator/workspace/server/openerp/osv/orm.py", line 476, in __getattr__
return self[name]
File "/home/administrator/workspace/server/openerp/osv/orm.py", line 391, in __getitem__
field_values = self._table.read(self._cr, self._uid, ids, field_names, context=self._context, load="_classic_write")
File "/home/administrator/workspace/server/openerp/osv/orm.py", line 3416, in read
result = self._read_flat(cr, user, select, fields, context, load)
File "/home/administrator/workspace/server/openerp/osv/orm.py", line 3476, in _read_flat
res.extend(cr.dictfetchall())
File "/usr/lib/python2.7/dist-packages/psycopg2/psycopg1.py", line 91, in dictfetchall
rows = _2cursor.fetchall(self)
MemoryError