Fix pgbench performance issue induced by commit af35fe5.

tglsfdc · tglsfdc · commit 5addea71c7c7 · 2025-02-07T13:41:43.000-05:00
Commit af35fe5 caused "pgbench -i" to emit a '\r' character for each data row loaded (when stderr is a terminal). That's effectively invisible on-screen, but it causes the connected terminal program to consume a lot of cycles. It's even worse if you're connected over ssh, as the data then has to pass through the ssh tunnel. Simplest fix is to move the added logic inside the if-tests that check whether to print a progress line. We could do it another way that avoids duplicating these few lines, but on the whole this seems the most transparent way to write it. Like the previous commit, back-patch to all supported versions. Reported-by: Andres Freund <andres@anarazel.de> Author: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: Nathan Bossart <nathandbossart@gmail.com> Discussion: https://postgr.es/m/4k4drkh7bcmdezq6zbkhp25mnrzpswqi2o75d5uv2eeg3aq6q7@b7kqdmzzwzgb Backpatch-through: 13
diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c
@@ -4312,6 +4312,16 @@ initGenerateDataClientSide(PGconn *con)
 							j, (int64) naccounts * scale,
 							(int) (((int64) j * 100) / (naccounts * (int64) scale)),
 							elapsed_sec, remaining_sec);
+
+			/*
+			 * 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;
 		}
 		/* let's not call the timing for each row, but only each 100 rows */
 		else if (use_quiet && (j % 100 == 0))
@@ -4326,20 +4336,20 @@ initGenerateDataClientSide(PGconn *con)
 								j, (int64) naccounts * scale,
 								(int) (((int64) j * 100) / (naccounts * (int64) scale)), elapsed_sec, remaining_sec);
 
+				/*
+				 * 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;
+
 				/* 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')
