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 "