Re: [HACKERS] Block level parallel vacuum

Hello

I noticed that parallel vacuum uses min_parallel_index_scan_size GUC to skip small indexes but this is not mentioned in
documentationfor both vacuum command and GUC itself.
 

+    /* Determine the number of parallel workers to launch */
+    if (lps->lvshared->for_cleanup)
+    {
+        if (lps->lvshared->first_time)
+            nworkers = lps->nindexes_parallel_cleanup +
+                lps->nindexes_parallel_condcleanup - 1;
+        else
+            nworkers = lps->nindexes_parallel_cleanup - 1;
+
+    }
+    else
+        nworkers = lps->nindexes_parallel_bulkdel - 1;

(lazy_parallel_vacuum_indexes)
Perhaps we need to add a comment for future readers, why we reduce the number of workers by 1. Maybe this would be
cleaner?

+    /* Determine the number of parallel workers to launch */
+    if (lps->lvshared->for_cleanup)
+    {
+        if (lps->lvshared->first_time)
+            nworkers = lps->nindexes_parallel_cleanup +
+                lps->nindexes_parallel_condcleanup;
+        else
+            nworkers = lps->nindexes_parallel_cleanup;
+
+    }
+    else
+        nworkers = lps->nindexes_parallel_bulkdel;
+
+   /* The leader process will participate */
+   nworkers--;

I have no more comments after reading the patches.

regards, Sergei