Fix aboriginal bug in BufFileDumpBuffer that would cause it to write the

tglsfdc · tglsfdc · commit 964ec46cfe95 · 2007-06-01T23:43:11.000Z
wrong data when dumping a bufferload that crosses a component-file boundary.
This probably has not been seen in the wild because (a) component files are
normally 1GB apiece and (b) non-block-aligned buffer usage is relatively
rare.  But it's fairly easy to reproduce a problem if one reduces RELSEG_SIZE
in a test build.  Kudos to Kurt Harriman for spotting the bug.
diff --git a/src/backend/storage/file/buffile.c b/src/backend/storage/file/buffile.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/file/buffile.c,v 1.25 2007/01/05 22:19:37 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/file/buffile.c,v 1.26 2007/06/01 23:43:11 tgl Exp $
  *
  * NOTES:
  *
@@ -289,7 +289,7 @@ BufFileDumpBuffer(BufFile *file)
 				return;			/* seek failed, give up */
 			file->offsets[file->curFile] = file->curOffset;
 		}
-		bytestowrite = FileWrite(thisfile, file->buffer, bytestowrite);
+		bytestowrite = FileWrite(thisfile, file->buffer + wpos, bytestowrite);
 		if (bytestowrite <= 0)
 			return;				/* failed to write */
 		file->offsets[file->curFile] += bytestowrite;

Original file line number	Diff line number	Diff line change
`@@ -7,7 +7,7 @@`
`7`	`7`	`* Portions Copyright (c) 1994, Regents of the University of California`
`8`	`8`	`*`
`9`	`9`	`* IDENTIFICATION`
`10`		`- * $PostgreSQL: pgsql/src/backend/storage/file/buffile.c,v 1.25 2007/01/05 22:19:37 momjian Exp $`
	`10`	`+ * $PostgreSQL: pgsql/src/backend/storage/file/buffile.c,v 1.26 2007/06/01 23:43:11 tgl Exp $`
`11`	`11`	`*`
`12`	`12`	`* NOTES:`
`13`	`13`	`*`
`@@ -289,7 +289,7 @@ BufFileDumpBuffer(BufFile *file)`
`289`	`289`	`return; /* seek failed, give up */`
`290`	`290`	`file->offsets[file->curFile] = file->curOffset;`
`291`	`291`	`}`
`292`		`- bytestowrite = FileWrite(thisfile, file->buffer, bytestowrite);`
	`292`	`+ bytestowrite = FileWrite(thisfile, file->buffer + wpos, bytestowrite);`
`293`	`293`	`if (bytestowrite <= 0)`
`294`	`294`	`return; /* failed to write */`
`295`	`295`	`file->offsets[file->curFile] += bytestowrite;`