VACUUM VERBOSE: Don't report "pages removed".

It doesn't make any sense to report this information, since VACUUM
VERBOSE reports on heap relation truncation directly.  This was an
oversight in commit 7ab96cf6, which made VACUUM VERBOSE output a little
more consistent with nearby autovacuum-specific log output.  Adjust
comments that describe how this is supposed to work in passing.

Also bring truncation-related VACUUM VERBOSE output in line with the
convention established for VACUUM VERBOSE output by commit f4f4a649.

Author: Peter Geoghegan <pg@bowt.ie>
Backpatch: 14-, where VACUUM VERBOSE's output changed.

src/backend/access/heap/vacuumlazy.c

@@ -1630,19 +1630,10 @@ lazy_scan_heap(LVRelState *vacrel, VacuumParams *params, bool aggressive)
 		update_index_statistics(vacrel);
 
 	/*
-	 * If table has no indexes and at least one heap pages was vacuumed, make
-	 * log report that lazy_vacuum_heap_rel would've made had there been
-	 * indexes (having indexes implies using the two pass strategy).
-	 *
-	 * We deliberately don't do this in the case where there are indexes but
-	 * index vacuuming was bypassed.  We make a similar report at the point
-	 * that index vacuuming is bypassed, but that's actually quite different
-	 * in one important sense: it shows information about work we _haven't_
-	 * done.
-	 *
-	 * log_autovacuum output does things differently; it consistently presents
-	 * information about LP_DEAD items for the VACUUM as a whole.  We always
-	 * report on each round of index and heap vacuuming separately, though.
+	 * When the table has no indexes (i.e. in the one-pass strategy case),
+	 * make log report that lazy_vacuum_heap_rel would've made had there been
+	 * indexes.  (As in the two-pass strategy case, only make this report when
+	 * there were LP_DEAD line pointers vacuumed in lazy_vacuum_heap_page.)
 	 */
 	if (vacrel->nindexes == 0 && vacrel->lpdead_item_pages > 0)
 		ereport(elevel,
@@ -1650,14 +1641,20 @@ lazy_scan_heap(LVRelState *vacrel, VacuumParams *params, bool aggressive)
 						vacrel->relname, (long long) vacrel->lpdead_items,
 						vacrel->lpdead_item_pages)));
 
+	/*
+	 * Make a log report summarizing pruning and freezing.
+	 *
+	 * The autovacuum specific logging in heap_vacuum_rel summarizes an entire
+	 * VACUUM operation, whereas each VACUUM VERBOSE log report generally
+	 * summarizes a single round of index/heap vacuuming (or rel truncation).
+	 * It wouldn't make sense to report on pruning or freezing while following
+	 * that convention, though.  You can think of this log report as a summary
+	 * of our first pass over the heap.
+	 */
 	initStringInfo(&buf);
 	appendStringInfo(&buf,
 					 _("%lld dead row versions cannot be removed yet, oldest xmin: %u\n"),
 					 (long long) vacrel->new_dead_tuples, vacrel->OldestXmin);
-	appendStringInfo(&buf, ngettext("%u page removed.\n",
-									"%u pages removed.\n",
-									vacrel->pages_removed),
-					 vacrel->pages_removed);
 	appendStringInfo(&buf, ngettext("Skipped %u page due to buffer pins, ",
 									"Skipped %u pages due to buffer pins, ",
 									vacrel->pinskipped_pages),
@@ -2379,6 +2376,7 @@ lazy_vacuum_heap_rel(LVRelState *vacrel)
 	 * We set all LP_DEAD items from the first heap pass to LP_UNUSED during
 	 * the second heap pass.  No more, no less.
 	 */
+	Assert(tupindex > 0);
 	Assert(vacrel->num_index_scans > 1 ||
 		   (tupindex == vacrel->lpdead_items &&
 			vacuumed_pages == vacrel->lpdead_item_pages));
@@ -3293,7 +3291,7 @@ lazy_truncate_heap(LVRelState *vacrel)
 		vacrel->rel_pages = new_rel_pages;
 
 		ereport(elevel,
-				(errmsg("\"%s\": truncated %u to %u pages",
+				(errmsg("table \"%s\": truncated %u to %u pages",
 						vacrel->relname,
 						old_rel_pages, new_rel_pages),
 				 errdetail_internal("%s",
@@ -3357,7 +3355,7 @@ count_nondeletable_pages(LVRelState *vacrel, bool *lock_waiter_detected)
 				if (LockHasWaitersRelation(vacrel->rel, AccessExclusiveLock))
 				{
 					ereport(elevel,
-							(errmsg("\"%s\": suspending truncate due to conflicting lock request",
+							(errmsg("table \"%s\": suspending truncate due to conflicting lock request",
 									vacrel->relname)));
 
 					*lock_waiter_detected = true;