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Adjust WAL code so that checkpoints truncate the xlog at the previous

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checkpoint's redo pointer, not its undo pointer, per discussion in
pghackers a few days ago.  No point in hanging onto undo information
until we have the ability to do something with it --- and this solves
a rather large problem with log space for long-running transactions.
Also, change all calls of write() to detect the case where write
returned a count less than requested, but failed to set errno.
Presume that this situation indicates ENOSPC, and give the appropriate
error message, rather than a random message associated with the previous
value of errno.
This commit is contained in:
Tom Lane
2001-06-06 17:07:46 +00:00
parent ce370eec35
commit 1173344e74
6 changed files with 76 additions and 20 deletions
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10
src/backend/utils/init/miscinit.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/init/miscinit.c,v 1.68 2001/06/01 20:27:41 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/init/miscinit.c,v 1.69 2001/06/06 17:07:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -659,13 +659,15 @@ CreateLockFile(const char *filename, bool amPostmaster,
snprintf(buffer, sizeof(buffer), "%d\n%s\n",
amPostmaster ? (int) my_pid : -((int) my_pid),
DataDir);
errno = 0;
if (write(fd, buffer, strlen(buffer)) != strlen(buffer))
{
int save_errno = errno;
close(fd);
unlink(filename);
errno = save_errno;
/* if write didn't set errno, assume problem is no disk space */
errno = save_errno ? save_errno : ENOSPC;
elog(FATAL, "Can't write lock file %s: %m", filename);
}
close(fd);
@@ -794,9 +796,13 @@ RecordSharedMemoryInLockFile(IpcMemoryKey shmKey, IpcMemoryId shmId)
* update should appear atomic to onlookers.
*/
len = strlen(buffer);
errno = 0;
if (lseek(fd, (off_t) 0, SEEK_SET) != 0 ||
(int) write(fd, buffer, len) != len)
{
/* if write didn't set errno, assume problem is no disk space */
if (errno == 0)
errno = ENOSPC;
elog(DEBUG, "Failed to write %s: %m", directoryLockFile);
close(fd);
return;