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 c4888a8a7656a54bd9818ccf7ce8bb604c10da02..b2729cd7d9164cc7a0c48d17ccfff0667811b97b 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
 }