Fix logging of pages skipped due to pins during vacuum.

anarazel · anarazel · commit 17eaae989778 · 2015-01-08T12:57:09.000+01:00
The new logging introduced in 35192f0 made the incorrect assumption that scan_all vacuums would always wait for buffer pins; but they only do so if the page actually needs to be frozen. Fix that inaccuracy by removing the difference in log output based on scan_all and just always remove the same message. I chose to keep the split log message from the original commit for now, it seems likely that it'll be of use in the future. Also merge the line about buffer pins in autovacuum's log output into the existing "pages: ..." line. It seems odd to have a separate line about pins, without the "topic: " prefix others have. Also rename the new 'pinned_pages' variable to 'pinskipped_pages' because it actually tracks the number of pages that could *not* be pinned. Discussion: 20150104005324.GC9626@awork2.anarazel.de
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
@@ -105,7 +105,7 @@ typedef struct LVRelStats
 	BlockNumber old_rel_pages;	/* previous value of pg_class.relpages */
 	BlockNumber rel_pages;		/* total number of pages */
 	BlockNumber scanned_pages;	/* number of pages we examined */
-	BlockNumber	pinned_pages;	/* # of pages we could not initially lock */
+	BlockNumber	pinskipped_pages; /* # of pages we skipped due to a pin */
 	double		scanned_tuples; /* counts only tuples on scanned pages */
 	double		old_rel_tuples; /* previous value of pg_class.reltuples */
 	double		new_rel_tuples; /* new estimated total # of tuples */
@@ -356,19 +356,10 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 							 get_namespace_name(RelationGetNamespace(onerel)),
 							 RelationGetRelationName(onerel),
 							 vacrelstats->num_index_scans);
-			appendStringInfo(&buf, _("pages: %u removed, %u remain\n"),
+			appendStringInfo(&buf, _("pages: %u removed, %u remain, %u skipped due to pins\n"),
 							 vacrelstats->pages_removed,
-							 vacrelstats->rel_pages);
-			if (vacrelstats->pinned_pages > 0)
-			{
-				if (scan_all)
-					appendStringInfo(&buf, _("waited for %u buffer pins\n"),
-									 vacrelstats->pinned_pages);
-				else
-					appendStringInfo(&buf,
-									 _("skipped %u pages due to buffer pins\n"),
-									 vacrelstats->pinned_pages);
-			}
+							 vacrelstats->rel_pages,
+							 vacrelstats->pinskipped_pages);
 			appendStringInfo(&buf,
 							 _("tuples: %.0f removed, %.0f remain, %.0f are dead but not yet removable\n"),
 							 vacrelstats->tuples_deleted,
@@ -634,8 +625,6 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 		/* We need buffer cleanup lock so that we can prune HOT chains. */
 		if (!ConditionalLockBufferForCleanup(buf))
 		{
-			vacrelstats->pinned_pages++;
-
 			/*
 			 * If we're not scanning the whole relation to guard against XID
 			 * wraparound, it's OK to skip vacuuming a page.  The next vacuum
@@ -644,6 +633,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 			if (!scan_all)
 			{
 				ReleaseBuffer(buf);
+				vacrelstats->pinskipped_pages++;
 				continue;
 			}
 
@@ -663,6 +653,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 			{
 				UnlockReleaseBuffer(buf);
 				vacrelstats->scanned_pages++;
+				vacrelstats->pinskipped_pages++;
 				continue;
 			}
 			LockBuffer(buf, BUFFER_LOCK_UNLOCK);
@@ -1129,15 +1120,8 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 					 nkeep);
 	appendStringInfo(&buf, _("There were %.0f unused item pointers.\n"),
 					 nunused);
-	if (vacrelstats->pinned_pages > 0)
-	{
-		if (scan_all)
-			appendStringInfo(&buf, _("Waited for %u buffer pins.\n"),
-							 vacrelstats->pinned_pages);
-		else
-			appendStringInfo(&buf, _("Skipped %u pages due to buffer pins.\n"),
-							 vacrelstats->pinned_pages);
-	}
+	appendStringInfo(&buf, _("Skipped %u pages due to buffer pins.\n"),
+					 vacrelstats->pinskipped_pages);
 	appendStringInfo(&buf, _("%u pages are entirely empty.\n"),
 					 empty_pages);
 	appendStringInfo(&buf, _("%s."),
