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

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.

diff --git a/contrib/dbase/dbf.c b/contrib/dbase/dbf.c
index 94f0b165cac063b5d23005ca82ca720ae4df2137..9ed0c475d12c164b2d194794274850b079f6a92f 100644 (file)
--- a/contrib/dbase/dbf.c
+++ b/contrib/dbase/dbf.c
@@ -155,9 +155,8 @@ int dbf_write_head(dbhead *dbh) {
        put_short(head.dbh_hlen, dbh->db_hlen);
        put_short(head.dbh_rlen, dbh->db_rlen);
        
-       if (write(dbh->db_fd, &head, sizeof(dbf_header)) == -1 ) {
+       if (write(dbh->db_fd, &head, sizeof(dbf_header)) != sizeof(dbf_header))
                return DBF_ERROR;
-       }
 
        return 0;
 }
@@ -180,14 +179,12 @@ int dbf_put_fields(dbhead *dbh) {
                field.dbf_flen = dbh->db_fields[t].db_flen;
                field.dbf_dec = dbh->db_fields[t].db_dec;
 
-               if (write(dbh->db_fd, &field, sizeof(dbf_field)) == -1) {
+               if (write(dbh->db_fd, &field, sizeof(dbf_field)) != sizeof(dbf_field))
                        return DBF_ERROR;
-               }
        }
 
-       if (write(dbh->db_fd, &end, 1) == -1) {
+       if (write(dbh->db_fd, &end, 1) != 1)
                return DBF_ERROR;
-       }
 
        return 0;
 }
@@ -457,15 +454,13 @@ int dbf_put_record(dbhead *dbh, field *rec, u_long where) {
          idx += rec[t].db_flen;
        }
 
-       if (write(dbh->db_fd, data, dbh->db_rlen) == -1) {
+       if (write(dbh->db_fd, data, dbh->db_rlen) != dbh->db_rlen)
                return DBF_ERROR;
-       }
 
 /* There's a 0x1A at the end of a dbf-file */
        if (where == dbh->db_records) {
-               if (write(dbh->db_fd, &end, 1) == -1) {
+               if (write(dbh->db_fd, &end, 1) != 1)
                        return DBF_ERROR;
-               }
        }
 
        dbh->db_offset += dbh->db_rlen;

diff --git a/contrib/pg_resetxlog/pg_resetxlog.c b/contrib/pg_resetxlog/pg_resetxlog.c
index 90fd3136dd8f09cf670ce75e4def2cac8074a49b..f8c81b5c55dddcb1ea3983f35eb1cf574dc5f40d 100644 (file)
--- a/contrib/pg_resetxlog/pg_resetxlog.c
+++ b/contrib/pg_resetxlog/pg_resetxlog.c
@@ -23,7 +23,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Header: /cvsroot/pgsql/contrib/pg_resetxlog/Attic/pg_resetxlog.c,v 1.4 2001/05/30 14:18:18 momjian Exp $
+ * $Header: /cvsroot/pgsql/contrib/pg_resetxlog/Attic/pg_resetxlog.c,v 1.5 2001/06/06 17:07:38 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -772,8 +772,12 @@ RewriteControlFile(void)
                exit(1);
        }
 
+       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;
                perror("RewriteControlFile failed to write pg_control file");
                exit(1);
        }
@@ -884,8 +888,12 @@ WriteEmptyXLOG(void)
                exit(1);
        }
 
+       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;
                perror("WriteEmptyXLOG: failed to write xlog file");
                exit(1);
        }
@@ -894,8 +902,11 @@ WriteEmptyXLOG(void)
        memset(buffer, 0, BLCKSZ);
        for (nbytes = BLCKSZ; nbytes < XLogSegSize; nbytes += BLCKSZ)
        {
+               errno = 0;
                if (write(fd, buffer, BLCKSZ) != BLCKSZ)
                {
+                       if (errno == 0)
+                               errno = ENOSPC;
                        perror("WriteEmptyXLOG: failed to write xlog file");
                        exit(1);
                }

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index abbdba9eb41cea543d9d1ff58693005b95eb2047..95e414c03c90025a262aff3b12faa083c8cddaf1 100644 (file)
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -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);
 
        /*

diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 06ee4bc2729b82def7bc585af37389f468f69e4d..237ae0a442807ba6238e6b12950d5037ab586d1d 100644 (file)
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/storage/file/fd.c,v 1.79 2001/05/30 14:15:26 momjian Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/storage/file/fd.c,v 1.80 2001/06/06 17:07:46 tgl Exp $
  *
  * NOTES:
  *
@@ -865,7 +865,14 @@ FileWrite(File file, char *buffer, int amount)
                           VfdCache[file].seekPos, amount, buffer));
 
        FileAccess(file);
+
+       errno = 0;
        returnCode = write(VfdCache[file].fd, buffer, amount);
+
+       /* if write didn't set errno, assume problem is no disk space */
+       if (returnCode != amount && errno == 0)
+               errno = ENOSPC;
+
        if (returnCode > 0)
                VfdCache[file].seekPos += returnCode;
        else

diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 36c0f6d43b42c8120e4419e70e330401dd2b7c81..762aceda73c28635908111abf9f94daa070d29bb 100644 (file)
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/storage/smgr/md.c,v 1.84 2001/05/10 20:38:49 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/storage/smgr/md.c,v 1.85 2001/06/06 17:07:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -582,8 +582,12 @@ mdblindwrt(RelFileNode rnode,
        status = SM_SUCCESS;
 
        /* write and optionally sync the block */
+       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(DEBUG, "mdblindwrt: write() failed: %m");
                status = SM_FAIL;
        }

diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index 544b57ff1d63707d3a0c489ac83b8fbd17733dc1..91711b26c36e7a3147521c48a7976cd9ae83d72f 100644 (file)
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -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;