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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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43
src/backend/access/transam/xlog.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.68 2001/06/03 14:53:56 petere Exp $
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.69 2001/06/06 17:07:38 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1068,9 +1068,15 @@ XLogWrite(XLogwrtRqst WriteRqst)
/* OK to write the page */
from = XLogCtl->pages + Write->curridx * BLCKSZ;
errno = 0;
if (write(openLogFile, from, BLCKSZ) != BLCKSZ)
{
/* if write didn't set errno, assume problem is no disk space */
if (errno == 0)
errno = ENOSPC;
elog(STOP, "write of log file %u, segment %u, offset %u failed: %m",
openLogId, openLogSeg, openLogOff);
}
openLogOff += BLCKSZ;
/*
@ -1323,6 +1329,7 @@ XLogFileInit(uint32 log, uint32 seg,
MemSet(zbuffer, 0, sizeof(zbuffer));
for (nbytes = 0; nbytes < XLogSegSize; nbytes += sizeof(zbuffer))
{
errno = 0;
if ((int) write(fd, zbuffer, sizeof(zbuffer)) != (int) sizeof(zbuffer))
{
int save_errno = errno;
@ -1332,7 +1339,8 @@ XLogFileInit(uint32 log, uint32 seg,
* space
*/
unlink(tmppath);
errno = save_errno;
/* if write didn't set errno, assume problem is no disk space */
errno = save_errno ? save_errno : ENOSPC;
elog(STOP, "ZeroFill failed to create or write %s: %m", tmppath);
}
@ -1990,8 +1998,14 @@ WriteControlFile(void)
elog(STOP, "WriteControlFile: could not create control file (%s): %m",
ControlFilePath);
errno = 0;
if (write(fd, buffer, BLCKSZ) != BLCKSZ)
{
/* if write didn't set errno, assume problem is no disk space */
if (errno == 0)
errno = ENOSPC;
elog(STOP, "WriteControlFile: write to control file failed: %m");
}
if (pg_fsync(fd) != 0)
elog(STOP, "WriteControlFile: fsync of control file failed: %m");
@ -2109,8 +2123,14 @@ UpdateControlFile(void)
if (fd < 0)
elog(STOP, "could not open control file (%s): %m", ControlFilePath);
errno = 0;
if (write(fd, ControlFile, sizeof(ControlFileData)) != sizeof(ControlFileData))
{
/* if write didn't set errno, assume problem is no disk space */
if (errno == 0)
errno = ENOSPC;
elog(STOP, "write to control file failed: %m");
}
if (pg_fsync(fd) != 0)
elog(STOP, "fsync of control file failed: %m");
@ -2248,8 +2268,14 @@ BootStrapXLOG(void)
use_existent = false;
openLogFile = XLogFileInit(0, 0, &use_existent, false);
errno = 0;
if (write(openLogFile, buffer, BLCKSZ) != BLCKSZ)
{
/* if write didn't set errno, assume problem is no disk space */
if (errno == 0)
errno = ENOSPC;
elog(STOP, "BootStrapXLOG failed to write log file: %m");
}
if (pg_fsync(openLogFile) != 0)
elog(STOP, "BootStrapXLOG failed to fsync log file: %m");
@ -2852,15 +2878,22 @@ CreateCheckPoint(bool shutdown)
elog(STOP, "concurrent transaction log activity while database system is shutting down");
/*
* Remember location of prior checkpoint's earliest info. Oldest item
* is redo or undo, whichever is older; but watch out for case that
* undo = 0.
* Select point at which we can truncate the log, which we base on the
* prior checkpoint's earliest info.
*
* With UNDO support: oldest item is redo or undo, whichever is older;
* but watch out for case that undo = 0.
*
* Without UNDO support: just use the redo pointer. This allows xlog
* space to be freed much faster when there are long-running transactions.
*/
#ifdef NOT_USED
if (ControlFile->checkPointCopy.undo.xrecoff != 0 &&
XLByteLT(ControlFile->checkPointCopy.undo,
ControlFile->checkPointCopy.redo))
XLByteToSeg(ControlFile->checkPointCopy.undo, _logId, _logSeg);
else
#endif
XLByteToSeg(ControlFile->checkPointCopy.redo, _logId, _logSeg);
/*