Fix bug in 2PC xact stats reporter

Author: kelvich

src/backend/postmaster/pgstat.c

@@ -2218,6 +2218,13 @@ pgstat_twophase_postcommit(TransactionId xid, uint16 info,
 	pgstat_info->t_counts.t_tuples_deleted += rec->tuples_deleted;
 	pgstat_info->t_counts.t_truncated = rec->t_truncated;
 
+	if (rec->t_truncated)
+	{
+		/* forget live/dead stats seen by backend thus far */
+		pgstat_info->t_counts.t_delta_live_tuples = 0;
+		pgstat_info->t_counts.t_delta_dead_tuples = 0;
+	}
+
 	pgstat_info->t_counts.t_delta_live_tuples +=
 		rec->tuples_inserted - rec->tuples_deleted;
 	pgstat_info->t_counts.t_delta_dead_tuples +=