VACUUM VERBOSE: Show dead items for an empty table.

petergeoghegan · petergeoghegan · commit bdb71dbe80d0 · 2022-04-15T14:20:56.000-07:00
Be consistent about the lines that VACUUM VERBOSE outputs by including an "index scan not needed: " line for completely empty tables. This makes the output more readable, especially with multiple distinct VACUUM operations processed by the same VACUUM command. It's also more consistent; even empty tables can use the failsafe, which wasn't reported in the standard way until now. Follow-up to commit 6e20f46, which taught VACUUM VERBOSE to be more consistent about reporting on scanned pages with empty tables.
diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
@@ -715,31 +715,29 @@ heap_vacuum_rel(Relation rel, VacuumParams *params,
 								 _("new relminmxid: %u, which is %d MXIDs ahead of previous value\n"),
 								 vacrel->NewRelminMxid, diff);
 			}
-			if (orig_rel_pages > 0)
+			if (vacrel->do_index_vacuuming)
 			{
-				if (vacrel->do_index_vacuuming)
-				{
-					if (vacrel->nindexes == 0 || vacrel->num_index_scans == 0)
-						appendStringInfoString(&buf, _("index scan not needed: "));
-					else
-						appendStringInfoString(&buf, _("index scan needed: "));
+				if (vacrel->nindexes == 0 || vacrel->num_index_scans == 0)
+					appendStringInfoString(&buf, _("index scan not needed: "));
+				else
+					appendStringInfoString(&buf, _("index scan needed: "));
 
-					msgfmt = _("%u pages from table (%.2f%% of total) had %lld dead item identifiers removed\n");
-				}
+				msgfmt = _("%u pages from table (%.2f%% of total) had %lld dead item identifiers removed\n");
+			}
+			else
+			{
+				if (!vacrel->failsafe_active)
+					appendStringInfoString(&buf, _("index scan bypassed: "));
 				else
-				{
-					if (!vacrel->failsafe_active)
-						appendStringInfoString(&buf, _("index scan bypassed: "));
-					else
-						appendStringInfoString(&buf, _("index scan bypassed by failsafe: "));
+					appendStringInfoString(&buf, _("index scan bypassed by failsafe: "));
 
-					msgfmt = _("%u pages from table (%.2f%% of total) have %lld dead item identifiers\n");
-				}
-				appendStringInfo(&buf, msgfmt,
-								 vacrel->lpdead_item_pages,
-								 100.0 * vacrel->lpdead_item_pages / orig_rel_pages,
-								 (long long) vacrel->lpdead_items);
+				msgfmt = _("%u pages from table (%.2f%% of total) have %lld dead item identifiers\n");
 			}
+			appendStringInfo(&buf, msgfmt,
+							 vacrel->lpdead_item_pages,
+							 orig_rel_pages == 0 ? 100.0 :
+							 100.0 * vacrel->lpdead_item_pages / orig_rel_pages,
+							 (long long) vacrel->lpdead_items);
 			for (int i = 0; i < vacrel->nindexes; i++)
 			{
 				IndexBulkDeleteResult *istat = vacrel->indstats[i];
