In relevant log messages, indicate whether vacuums are aggressive.

Kyotaro Horiguchi, reviewed Masahiko Sawada, David G. Johnston, Álvaro
Herrera, and me.  Grammar correction to the final posted patch by me.

Discussion: http://postgr.es/m/20170329.124649.193656100.horiguchi.kyotaro@lab.ntt.co.jp

src/backend/commands/vacuumlazy.c

@@ -355,6 +355,7 @@ lazy_vacuum_rel(Relation onerel, int options, VacuumParams *params,
 									   params->log_min_duration))
 		{
 			StringInfoData buf;
+			char *msgfmt;
 
 			TimestampDifference(starttime, endtime, &secs, &usecs);
 
@@ -373,7 +374,11 @@ lazy_vacuum_rel(Relation onerel, int options, VacuumParams *params,
 			 * emitting individual parts of the message when not applicable.
 			 */
 			initStringInfo(&buf);
-			appendStringInfo(&buf, _("automatic vacuum of table \"%s.%s.%s\": index scans: %d\n"),
+			if (aggressive)
+				msgfmt = _("automatic aggressive vacuum of table \"%s.%s.%s\": index scans: %d\n");
+			else
+				msgfmt = _("automatic vacuum of table \"%s.%s.%s\": index scans: %d\n");
+			appendStringInfo(&buf, msgfmt,
 							 get_database_name(MyDatabaseId),
 							 get_namespace_name(RelationGetNamespace(onerel)),
 							 RelationGetRelationName(onerel),
@@ -486,6 +491,12 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 	pg_rusage_init(&ru0);
 
 	relname = RelationGetRelationName(onerel);
+	if (aggressive)
+		ereport(elevel,
+				(errmsg("aggressively vacuuming \"%s.%s\"",
+						get_namespace_name(RelationGetNamespace(onerel)),
+						relname)));
+	else
 		ereport(elevel,
 				(errmsg("vacuuming \"%s.%s\"",
 						get_namespace_name(RelationGetNamespace(onerel)),