将连接表移出主查询：

SELECT af.ID, af.nom_flux, st.chemin_stockage, af.hash_flux 
FROM JOIN stockage st 
INNER JOIN allotissement_flux af 
   ON EXISTS ( SELECT *
        FROM signature sig
        WHERE st.id_flux = sig.id_flux
        AND af.ID = sig.id_flux
        AND sig.statut_signature = 'A_SIGNER'
        AND sig.nb_appel_service_signature < 4 
        AND sig.date_statut_signature >= sysdate - 100
        )
WHERE st.statut_stockage = 'OUI'
AND st.date_statut_stockage >= sysdate - 100
        ;

首先，你应该替换 DISTINCT 与 WINDOW 条款。
此外，还可以对sql进行一些重构，以提高其性能。因为您没有从中选取任何列 signature 但是，您正在基于此表筛选某些记录。让我们在连接自身时应用这些过滤器。它可能会带来一些改善执行时间。
示例sql-

SELECT ID, nom_flux, chemin_stockage, hash_flux FROM (SELECT af.ID, af.nom_flux, st.chemin_stockage, af.hash_flux, rank() over (partition by af.ID, af.nom_flux, st.chemin_stockage, af.hash_flux order by af.ID) as rrank
FROM allotissement_flux af   
INNER JOIN stockage st ON st.id_flux = sig.id_flux AND st.date_statut_stockage >= sysdate - 100 AND st.statut_stockage = 'OUI'
INNER JOIN signature sig ON af.ID = sig.id_flux  AND sig.date_statut_signature >= sysdate - 100 AND sig.statut_signature = 'A_SIGNER' AND sig.nb_appel_service_signature < 4)) WHERE rrank = 1;