On N elements resource.calendar.leave and M elements resource.resource recordsets, the __get__ calls to 4 leave fields were done M time per loop, aka 4*N*M times. This commit reduces the number of call to 4*N times, reducing the method executing time for grid_unavailability from 9 seconds to +- 4.5 on odoo.com while displaying all timesheets on Month view. closes odoo/odoo#150408 Related: odoo/enterprise#54830 Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>