Remove wal_files - Mailing list pgsql-hackers

We have the TODO item:

  * Remove wal_files postgresql.conf option because WAL files are now recycled

The following patch completes this item.  It also makes the WAL
documentation a lot easier to understand.  ;-)

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073
Index: doc/src/sgml/runtime.sgml
===================================================================
RCS file: /cvsroot/pgsql-server/doc/src/sgml/runtime.sgml,v
retrieving revision 1.128
diff -c -c -r1.128 runtime.sgml
*** doc/src/sgml/runtime.sgml    29 Aug 2002 19:53:58 -0000    1.128
--- doc/src/sgml/runtime.sgml    30 Aug 2002 03:46:18 -0000
***************
*** 1949,1965 ****
       </varlistentry>

       <varlistentry>
-       <term><varname>WAL_FILES</varname> (<type>integer</type>)</term>
-       <listitem>
-        <para>
-         Number of log files that are created in advance at checkpoint
-         time.  This option can only be set at server start or in the
-     <filename>postgresql.conf</filename> file.
-        </para>
-       </listitem>
-      </varlistentry>
-
-      <varlistentry>
        <term><varname>WAL_SYNC_METHOD</varname> (<type>string</type>)</term>
        <listitem>
         <para>
--- 1949,1954 ----
Index: doc/src/sgml/wal.sgml
===================================================================
RCS file: /cvsroot/pgsql-server/doc/src/sgml/wal.sgml,v
retrieving revision 1.16
diff -c -c -r1.16 wal.sgml
*** doc/src/sgml/wal.sgml    5 Jul 2002 19:06:11 -0000    1.16
--- doc/src/sgml/wal.sgml    30 Aug 2002 03:46:18 -0000
***************
*** 276,284 ****
     By default a new 16MB segment file is created only if more than 75% of
     the current segment has been used.  This is inadequate if the system
     generates more than 4MB of log output between checkpoints.
-    One can instruct the server to pre-create up to 64 log segments
-    at checkpoint time by modifying the <varname>WAL_FILES</varname>
-    configuration parameter.
    </para>

    <para>
--- 276,281 ----
***************
*** 306,325 ****

    <para>
     The number of 16MB segment files will always be at least
!    <varname>WAL_FILES</varname> + 1, and will normally not exceed
!    <varname>WAL_FILES</varname> + MAX(<varname>WAL_FILES</varname>,
!    <varname>CHECKPOINT_SEGMENTS</varname>) + 1. This may be used to
!    estimate space requirements for WAL. Ordinarily, when an old log
!    segment files are no longer needed, they are recycled (renamed to
!    become the next sequential future segments). If, due to a short-term
!    peak of log output rate, there are more than
!    <varname>WAL_FILES</varname> + MAX(<varname>WAL_FILES</varname>,
!    <varname>CHECKPOINT_SEGMENTS</varname>) + 1 segment files, then
!    unneeded segment files will be deleted instead of recycled until the
!    system gets back under this limit. (If this happens on a regular
!    basis, <varname>WAL_FILES</varname> should be increased to avoid it.
!    Deleting log segments that will only have to be created again later
!    is expensive and pointless.)
    </para>

    <para>
--- 303,316 ----

    <para>
     The number of 16MB segment files will always be at least
!    1, and will normally not exceed <varname>CHECKPOINT_SEGMENTS</varname>)
!    + 1.  This may be used to estimate space requirements for WAL.
!    Ordinarily, when old log segment files are no longer needed,
!    they are recycled (renamed to become the next sequential future
!    segments). If, due to a short-term peak of log output rate, there
!    are more than <varname>CHECKPOINT_SEGMENTS</varname>) + 1 segment files,
!    the unneeded segment files will be deleted instead of recycled until the
!    system gets back under this limit.
    </para>

    <para>
Index: src/backend/access/transam/xlog.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/access/transam/xlog.c,v
retrieving revision 1.102
diff -c -c -r1.102 xlog.c
*** src/backend/access/transam/xlog.c    17 Aug 2002 15:12:06 -0000    1.102
--- src/backend/access/transam/xlog.c    30 Aug 2002 03:46:21 -0000
***************
*** 87,93 ****
  /* User-settable parameters */
  int            CheckPointSegments = 3;
  int            XLOGbuffers = 8;
- int            XLOGfiles = 0;        /* # of files to preallocate during ckpt */
  int            XLOG_DEBUG = 0;
  char       *XLOG_sync_method = NULL;
  const char    XLOG_sync_method_default[] = DEFAULT_SYNC_METHOD_STR;
--- 87,92 ----
***************
*** 97,103 ****
  /*
   * XLOGfileslop is used in the code as the allowed "fuzz" in the number of
   * preallocated XLOG segments --- we try to have at least XLOGfiles advance
!  * segments but no more than XLOGfiles+XLOGfileslop segments.  This could
   * be made a separate GUC variable, but at present I think it's sufficient
   * to hardwire it as 2*CheckPointSegments+1.  Under normal conditions, a
   * checkpoint will free no more than 2*CheckPointSegments log segments, and
--- 96,102 ----
  /*
   * XLOGfileslop is used in the code as the allowed "fuzz" in the number of
   * preallocated XLOG segments --- we try to have at least XLOGfiles advance
!  * segments but no more than XLOGfileslop segments.  This could
   * be made a separate GUC variable, but at present I think it's sufficient
   * to hardwire it as 2*CheckPointSegments+1.  Under normal conditions, a
   * checkpoint will free no more than 2*CheckPointSegments log segments, and
***************
*** 1422,1428 ****
       * ours to pre-create a future log segment.
       */
      if (!InstallXLogFileSegment(log, seg, tmppath,
!                                 *use_existent, XLOGfiles + XLOGfileslop,
                                  use_lock))
      {
          /* No need for any more future segments... */
--- 1421,1427 ----
       * ours to pre-create a future log segment.
       */
      if (!InstallXLogFileSegment(log, seg, tmppath,
!                                 *use_existent, XLOGfileslop,
                                  use_lock))
      {
          /* No need for any more future segments... */
***************
*** 1568,1587 ****
      uint32        _logSeg;
      int            lf;
      bool        use_existent;
-     int            i;

      XLByteToPrevSeg(endptr, _logId, _logSeg);
!     if (XLOGfiles > 0)
!     {
!         for (i = 1; i <= XLOGfiles; i++)
!         {
!             NextLogSeg(_logId, _logSeg);
!             use_existent = true;
!             lf = XLogFileInit(_logId, _logSeg, &use_existent, true);
!             close(lf);
!         }
!     }
!     else if ((endptr.xrecoff - 1) % XLogSegSize >=
               (uint32) (0.75 * XLogSegSize))
      {
          NextLogSeg(_logId, _logSeg);
--- 1567,1575 ----
      uint32        _logSeg;
      int            lf;
      bool        use_existent;

      XLByteToPrevSeg(endptr, _logId, _logSeg);
!     if ((endptr.xrecoff - 1) % XLogSegSize >=
               (uint32) (0.75 * XLogSegSize))
      {
          NextLogSeg(_logId, _logSeg);
***************
*** 1635,1645 ****
                  /*
                   * Before deleting the file, see if it can be recycled as
                   * a future log segment.  We allow recycling segments up
!                  * to XLOGfiles + XLOGfileslop segments beyond the current
                   * XLOG location.
                   */
                  if (InstallXLogFileSegment(endlogId, endlogSeg, path,
!                                            true, XLOGfiles + XLOGfileslop,
                                             true))
                  {
                      elog(LOG, "recycled transaction log file %s",
--- 1623,1633 ----
                  /*
                   * Before deleting the file, see if it can be recycled as
                   * a future log segment.  We allow recycling segments up
!                  * to XLOGfileslop segments beyond the current
                   * XLOG location.
                   */
                  if (InstallXLogFileSegment(endlogId, endlogSeg, path,
!                                            true, XLOGfileslop,
                                             true))
                  {
                      elog(LOG, "recycled transaction log file %s",
Index: src/backend/utils/misc/guc.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/utils/misc/guc.c,v
retrieving revision 1.87
diff -c -c -r1.87 guc.c
*** src/backend/utils/misc/guc.c    29 Aug 2002 21:02:12 -0000    1.87
--- src/backend/utils/misc/guc.c    30 Aug 2002 03:46:23 -0000
***************
*** 641,651 ****
      },

      {
-         { "wal_files", PGC_SIGHUP }, &XLOGfiles,
-         0, 0, 64, NULL, NULL
-     },
-
-     {
          { "wal_debug", PGC_SUSET }, &XLOG_DEBUG,
          0, 0, 16, NULL, NULL
      },
--- 641,646 ----
Index: src/include/access/xlog.h
===================================================================
RCS file: /cvsroot/pgsql-server/src/include/access/xlog.h,v
retrieving revision 1.35
diff -c -c -r1.35 xlog.h
*** src/include/access/xlog.h    17 Aug 2002 15:12:07 -0000    1.35
--- src/include/access/xlog.h    30 Aug 2002 03:46:23 -0000
***************
*** 185,191 ****
  /* these variables are GUC parameters related to XLOG */
  extern int    CheckPointSegments;
  extern int    XLOGbuffers;
- extern int    XLOGfiles;
  extern int    XLOG_DEBUG;
  extern char *XLOG_sync_method;
  extern const char XLOG_sync_method_default[];
--- 185,190 ----