Skip second WriteToc() call for custom-format dumps without data.

nathan-bossart · nathan-bossart · commit e3cc039a7d93 · 2025-04-04T14:51:08.000-05:00
Presently, "pg_dump --format=custom" calls WriteToc() twice. The second call updates the data offset information, which allegedly makes parallel pg_restore significantly faster. However, if we're not dumping any data, there are no data offsets to update, so we can skip this step. Reviewed-by: Jeff Davis <pgsql@j-davis.com> Discussion: https://postgr.es/m/Z9c1rbzZegYQTOQE%40nathan
diff --git a/src/bin/pg_dump/pg_backup_custom.c b/src/bin/pg_dump/pg_backup_custom.c
@@ -755,9 +755,11 @@ _CloseArchive(ArchiveHandle *AH)
 		 * If possible, re-write the TOC in order to update the data offset
 		 * information.  This is not essential, as pg_restore can cope in most
 		 * cases without it; but it can make pg_restore significantly faster
-		 * in some situations (especially parallel restore).
+		 * in some situations (especially parallel restore).  We can skip this
+		 * step if we're not dumping any data; there are no offsets to update
+		 * in that case.
 		 */
-		if (ctx->hasSeek &&
+		if (ctx->hasSeek && AH->public.dopt->dumpData &&
 			fseeko(AH->FH, tpos, SEEK_SET) == 0)
 			WriteToc(AH);
 	}
