MT#16321 More narrow conditions for subquery to improve billing_mappings speed

Change-Id: I4c86b84b1e49edcdcadd134f9e2acb0792f02822

lib/NGCP/Schema/Result/billing_mappings_actual.pm

@@ -61,6 +61,7 @@ select bm.contract_id,max(bm.id) as actual_bm_id from billing.billing_mappings b
         from billing.billing_mappings bmm 
         where ( bmm.`end_date` >= ? OR bmm.`end_date` IS NULL ) 
             AND ( bmm.`start_date` <= ? OR bmm.`start_date` IS NULL ) 
+            AND ( ? is null OR bmm.`contract_id` = ? ) 
         group by bmm.contract_id
     ) bmm on bm.contract_id=bmm.contract_id and (bm.start_date=bmm.max_start_date or (bmm.max_start_date is null and bm.start_date is null)) 
 group by  bm.contract_id