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Comment out FileUnlink of excess segments during mdtruncate().

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This is unsafe in 6.5 because other backends may be able to access the file
before noticing the shared cache inval message that tells 'em to re-open
the file.  We have fixed this for 6.6 but the changes seem too risky to
back-patch for 6.5.2.
Also, back-patch Tatsuo's change to prevent creation of files during
mdopen().
This commit is contained in:
Tom Lane
1999-09-06 20:00:15 +00:00
parent 958e45a84b
commit 60c3ccffbe
1 changed files with 23 additions and 4 deletions
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27
src/backend/storage/smgr/md.c
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@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/smgr/md.c,v 1.46.2.1 1999/09/02 04:07:16 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/smgr/md.c,v 1.46.2.2 1999/09/06 20:00:15 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -284,13 +284,23 @@ mdopen(Relation reln)
fd = FileNameOpenFile(path, O_RDWR | O_BINARY, 0600);
#endif
/* this should only happen during bootstrap processing */
if (fd < 0)
{
/* in bootstrap mode, accept mdopen as substitute for mdcreate */
if (IsBootstrapProcessingMode())
{
#ifndef __CYGWIN32__
fd = FileNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL, 0600);
fd = FileNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL, 0600);
#else
fd = FileNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL | O_BINARY, 0600);
fd = FileNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL | O_BINARY, 0600);
#endif
}
if (fd < 0)
{
elog(ERROR, "mdopen: couldn't open %s: %m", path);
return -1;
}
}
vfd = _fdvec_alloc();
if (vfd < 0)
@@ -755,7 +765,16 @@ mdtruncate(Relation reln, int nblocks)
* a big file...
*/
FileTruncate(v->mdfd_vfd, 0);
/* In 6.5, it is not safe to unlink apparently-unused segments,
* because another backend could store tuples in one of those
* segments before it notices the shared-cache-invalidation
* message that would warn it to re-open the file. So, don't
* unlink 'em, just truncate 'em. This is fixed properly for 6.6
* but back-patching the changes was judged too risky.
*/
#if 0
FileUnlink(v->mdfd_vfd);
#endif
v = v->mdfd_chain;
Assert(ov != &Md_fdvec[fd]); /* we never drop the 1st segment */
pfree(ov);