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

@@ -4222,6 +4222,8 @@ initGenerateDataClientSide(PGconn *con)
 	PGresult   *res;
 	int			i;
 	int64		k;
+	int			chars = 0;
+	int			prev_chars = 0;
 
 	/* used to track elapsed time and estimate of the remaining time */
 	pg_time_usec_t start;
@@ -4304,10 +4306,10 @@ initGenerateDataClientSide(PGconn *con)
 			double		elapsed_sec = PG_TIME_GET_DOUBLE(pg_time_now() - start);
 			double		remaining_sec = ((double) scale * naccounts - j) * elapsed_sec / j;
 
-			fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) done (elapsed %.2f s, remaining %.2f s)%c",
-					j, (int64) naccounts * scale,
-					(int) (((int64) j * 100) / (naccounts * (int64) scale)),
-					elapsed_sec, remaining_sec, eol);
+			chars = fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) done (elapsed %.2f s, remaining %.2f s)",
+							j, (int64) naccounts * scale,
+							(int) (((int64) j * 100) / (naccounts * (int64) scale)),
+							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))
@@ -4318,14 +4320,24 @@ initGenerateDataClientSide(PGconn *con)
 			/* have we reached the next interval (or end)? */
 			if ((j == scale * naccounts) || (elapsed_sec >= log_interval * LOG_STEP_SECONDS))
 			{
-				fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) done (elapsed %.2f s, remaining %.2f s)%c",
-						j, (int64) naccounts * scale,
-						(int) (((int64) j * 100) / (naccounts * (int64) scale)), elapsed_sec, remaining_sec, eol);
+				chars = fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) done (elapsed %.2f s, remaining %.2f s)",
+								j, (int64) naccounts * scale,
+								(int) (((int64) j * 100) / (naccounts * (int64) scale)), 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 (eol != '\n')