abnormal overload when I click on "search more"

Hello,
I work on a project with a heavy large database(175000 partners, 38000 products ...), openerp is stable, but when I click on "search more" anywhere for partners and products fields , the server lose more than 50% of free ram (7/12 Go) on monothread. ( http://img15.hostingpics.net/pics/309320Sanstitre.png )
On mutilthread (three workers on configuration file), the server causes this error :

Client Traceback (most recent call last):
  File "/home/openerp/OpenERP_OCB/web/addons/web/http.py", line 204, in dispatch
    response["result"] = method(self, **self.params)
  File "/home/openerp/OpenERP_OCB/web/addons/web/controllers/main.py", line 1128, in call_kw
    return self._call_kw(req, model, method, args, kwargs)
  File "/home/openerp/OpenERP_OCB/web/addons/web/controllers/main.py", line 1120, in _call_kw
    return getattr(req.session.model(model), method)(*args, **kwargs)
  File "/home/openerp/OpenERP_OCB/web/addons/web/session.py", line 42, in proxy
    result = self.proxy.execute_kw(self.session._db, self.session._uid, self.session._password, self.model, method, args, kw)
  File "/home/openerp/OpenERP_OCB/web/addons/web/session.py", line 30, in proxy_method
    result = self.session.send(self.service_name, method, *args)
  File "/home/openerp/OpenERP_OCB/web/addons/web/session.py", line 103, in send
    raise xmlrpclib.Fault(openerp.tools.ustr(e), formatted_info)

Server Traceback (most recent call last):
  File "/home/openerp/OpenERP_OCB/web/addons/web/session.py", line 89, in send
    return openerp.netsvc.dispatch_rpc(service_name, method, args)
  File "/home/openerp/OpenERP_OCB/server/openerp/netsvc.py", line 292, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/home/openerp/OpenERP_OCB/server/openerp/service/web_services.py", line 626, in dispatch
    res = fn(db, uid, *params)
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/osv.py", line 188, in execute_kw
    return self.execute(db, uid, obj, method, *args, **kw or {})
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/osv.py", line 131, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/osv.py", line 197, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/home/openerp/OpenERP_OCB/addons/audittrail/audittrail.py", line 514, in execute_cr
    return fct_src(cr, uid, model, method, *args, **kw)
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/osv.py", line 185, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/home/openerp/OpenERP_OCB/server/openerp/addons/base/res/res_partner.py", line 635, in name_search
    return super(res_partner,self).name_search(cr, uid, name, args, operator=operator, context=context, limit=limit)
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/orm.py", line 2412, in name_search
    return self._name_search(cr, user, name, args, operator, context, limit)
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/orm.py", line 2444, in _name_search
    res = self.name_get(cr, access_rights_uid, ids, context)
  File "/home/openerp/addons_kevin/tetra_partner/partner.py", line 365, in name_get
    res = super(res_partner, self).name_get(cr, uid, ids, context=context)
  File "/home/openerp/OpenERP_OCB/server/openerp/addons/base/res/res_partner.py", line 545, in name_get
    name = record.name
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/orm.py", line 497, in __getattr__
    return self[name]
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/orm.py", line 405, in __getitem__
    field_values = self._table.read(self._cr, self._uid, ids, field_names, context=self._context, load="_classic_write")
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/orm.py", line 3624, in read
    result = self._read_flat(cr, user, select, fields, context, load)
  File "/home/openerp/OpenERP_OCB/server/openerp/osv/orm.py", line 3677, in _read_flat
    results = cr.dictfetchall()
  File "/usr/lib/python2.7/dist-packages/psycopg2/psycopg1.py", line 93, in dictfetchall
    res.append(self.__build_dict(row))
  File "/usr/lib/python2.7/dist-packages/psycopg2/psycopg1.py", line 72, in __build_dict
    res[self.description[i][0]] = row[i]
MemoryError

Have you ever had the scenario?

thank you for your help