VACUUM VERBOSE: tweak scanned_pages logic.

Commit 872770fd6c taught VACUUM VERBOSE and autovacuum logging to
display the total number of pages scanned by VACUUM.  This information
was also displayed as a percentage of rel_pages in parenthesis, which
makes it easy to spot trends over time and across tables.

The instrumentation displayed "0 scanned (0.00% of total)" for totally
empty tables.  Tweak the instrumentation: have it show "0 scanned
(100.00% of total)" for empty tables instead.  This approach is clearer
and more consistent.

diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index 620b7a7af5bd6c0b8c7e335e07581b196ba26dd8..87ab7775aee7a84c4e1915c88494c265e2ef254f 100644 (file)
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -676,7 +676,7 @@ heap_vacuum_rel(Relation rel, VacuumParams *params,
                                                         vacrel->removed_pages,
                                                         vacrel->rel_pages,
                                                         vacrel->scanned_pages,
-                                                        orig_rel_pages == 0 ? 0 :
+                                                        orig_rel_pages == 0 ? 100.0 :
                                                         100.0 * vacrel->scanned_pages / orig_rel_pages);
                        appendStringInfo(&buf,
                                                         _("tuples: %lld removed, %lld remain, %lld are dead but not yet removable\n"),