In pg_upgrade, add C comment about how autovacuum is disabled.

diff --git a/contrib/pg_upgrade/server.c b/contrib/pg_upgrade/server.c
index 84bd03ed8ed55d564c1be6d3f7d8b06e8ffbc87a..4d5f37301b46ba35525eb0280e4e2717f7e739c1 100644 (file)
--- a/contrib/pg_upgrade/server.c
+++ b/contrib/pg_upgrade/server.c
@@ -169,7 +169,11 @@ start_postmaster(ClusterInfo *cluster, bool quiet)
         * same file because we get the error: "The process cannot access the file
         * because it is being used by another process." so we have to send all
         * other output to 'nul'.
-        */
+        *
+        * Using autovacuum=off disables cleanup vacuum and analyze, but
+        * freeze vacuums can still happen, so we set
+        * autovacuum_freeze_max_age high too.
+        */     
        snprintf(cmd, sizeof(cmd),
                         SYSTEMQUOTE "\"%s/pg_ctl\" -l \"%s\" -D \"%s\" "
                         "-o \"-p %d -c autovacuum=off "