SQL & PL/SQL :: UNION ALL - View With Similar Indexes Each Table?

I have this sql (generated by discoverer plus), and work fine:

SELECT COUNT(o10475761.SUC_ID)
FROM GAR_DW.ARTICULOS o10475528,
GAR_DW.EMPRESAS o10475602,
GAR_DW.L_DIA o10475639,

[code]...

We need change the table stock_por_sucursal for a view like this, with similar indexes each table

select * from stock_por_sucursal_old
union all
select * from stock_por_sucursal_new

and the result is not good:

SQL Statement from editor:

SELECT COUNT(o10475761.SUC_ID)
FROM GAR_DW.ARTICULOS o10475528,
GAR_DW.EMPRESAS o10475602,
GAR_DW.L_DIA o10475639,
GAR_DW.V_STOCK_POR_SUCURSAL o10475761,

[code]...

finally add a HINT /*+ gather_plan_statistics push_pred(TABLE) */ and the result was not very good in this case, but improved the resolution of the view, the rest got worse

SQL Statement from editor:
SELECT /*+ gather_plan_statistics push_pred(o10475761) */ COUNT(o10475761.SUC_ID)
FROM GAR_DW.ARTICULOS o10475528,
GAR_DW.EMPRESAS o10475602,
GAR_DW.L_DIA o10475639,

[code]...