pgbench: Ensure previous progress message is fully cleared when updating.

During pgbench's table initialization, progress updates could display
leftover characters from the previous message if the new message
was shorter. This commit resolves the issue by appending spaces to
the current message to fully overwrite any remaining characters from
the previous line.

Back-patch to all the supported versions.

Author: Yushi Ogiwara, Tatsuo Ishii, Fujii Masao
Reviewed-by: Tatsuo Ishii, Fujii Masao
Discussion: https://postgr.es/m/9a9b8b95b6a709877ae48ad5b0c59bb9@oss.nttdata.com

src/bin/pgbench/pgbench.c

@@ -4944,6 +4944,7 @@ initPopulateTable(PGconn *con, const char *table, int64 base,
 	int			n;
 	int64		k;
 	int			chars = 0;
+	int			prev_chars = 0;
 	PGresult   *res;
 	PQExpBufferData sql;
 	char		copy_statement[256];
@@ -5004,10 +5005,10 @@ initPopulateTable(PGconn *con, const char *table, int64 base,
 			double		elapsed_sec = PG_TIME_GET_DOUBLE(pg_time_now() - start);
 			double		remaining_sec = ((double) total - j) * elapsed_sec / j;
 
-			chars = fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) of %s done (elapsed %.2f s, remaining %.2f s)%c",
+			chars = fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) of %s done (elapsed %.2f s, remaining %.2f s)",
 							j, total,
 							(int) ((j * 100) / total),
-							table, elapsed_sec, remaining_sec, eol);
+							table, elapsed_sec, remaining_sec);
 		}
 		/* let's not call the timing for each row, but only each 100 rows */
 		else if (use_quiet && (j % 100 == 0))
@@ -5018,19 +5019,29 @@ initPopulateTable(PGconn *con, const char *table, int64 base,
 			/* have we reached the next interval (or end)? */
 			if ((j == total) || (elapsed_sec >= log_interval * LOG_STEP_SECONDS))
 			{
-				chars = fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) of %s done (elapsed %.2f s, remaining %.2f s)%c",
+				chars = fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) of %s done (elapsed %.2f s, remaining %.2f s)",
 								j, total,
 								(int) ((j * 100) / total),
-								table, elapsed_sec, remaining_sec, eol);
+								table, elapsed_sec, remaining_sec);
 
 				/* skip to the next interval */
 				log_interval = (int) ceil(elapsed_sec / LOG_STEP_SECONDS);
 			}
 		}
+
+		/*
+		 * If the previous progress message is longer than the current one,
+		 * add spaces to the current line to fully overwrite any remaining
+		 * characters from the previous message.
+		 */
+		if (prev_chars > chars)
+			fprintf(stderr, "%*c", prev_chars - chars, ' ');
+		fputc(eol, stderr);
+		prev_chars = chars;
 	}
 
 	if (chars != 0 && eol != '\n')
-		fprintf(stderr, "%*c\r", chars - 1, ' ');	/* Clear the current line */
+		fprintf(stderr, "%*c\r", chars, ' ');	/* Clear the current line */
 
 	if (PQputline(con, "\\.\n"))
 		pg_fatal("very last PQputline failed");