Limit depth of forced recursion for CLOBBER_CACHE_RECURSIVELY.

It's somewhat surprising that we got away with this before.  (Actually,
since nobody tests this routinely AFAIK, it might've been broken for
awhile.  But it's definitely broken in the wake of commit f868a8143.)
It seems sufficient to limit the forced recursion to a small number
of levels.

Back-patch to all supported branches, like the preceding patch.

Discussion: https://postgr.es/m/12259.1532117714@sss.pgh.pa.us

diff --git a/src/backend/utils/cache/inval.c b/src/backend/utils/cache/inval.c
index f0c261208738f621213ccbb3c57d2b62d7c831de..ca283f82d2ef0c9acbd3e50e0e87d7ae3ad6e75d 100644 (file)
--- a/src/backend/utils/cache/inval.c
+++ b/src/backend/utils/cache/inval.c
@@ -699,7 +699,17 @@ AcceptInvalidationMessages(void)
        }
    }
 #elif defined(CLOBBER_CACHE_RECURSIVELY)
-   InvalidateSystemCaches();
+   {
+       static int  recursion_depth = 0;
+
+       /* Maximum depth is arbitrary depending on your threshold of pain */
+       if (recursion_depth < 3)
+       {
+           recursion_depth++;
+           InvalidateSystemCaches();
+           recursion_depth--;
+       }
+   }
 #endif
 }