pg_resetxlog: add option to set oldest xid & use by pg_upgrade

Add pg_resetxlog -u option to set the oldest xid in pg_control.
Previously -x set this value be -2 billion less than the -x value.
However, this causes the server to immediately scan all relation's
relfrozenxid so it can advance pg_control's oldest xid to be inside the
autovacuum_freeze_max_age range, which is inefficient and might disrupt
diagnostic recovery.  pg_upgrade will use this option to better create
the new cluster to match the old cluster.

Reported-by: Jason Harvey, Floris Van Nee
Discussion: https://postgr.es/m/20190615183759.GB239428@rfd.leadboat.com, 87da83168c644fd9aae38f546cc70295@opammb0562.comp.optiver.com

Author: Bertrand Drouvot

Backpatch-through: 9.6

diff --git a/doc/src/sgml/ref/pg_resetwal.sgml b/doc/src/sgml/ref/pg_resetwal.sgml
index b3b750e722a43fb8f0916ae01bf80186d257342d..3e4882cdc65dd82d1a1c548d530c7aa007b9ff40 100644 (file)
--- a/doc/src/sgml/ref/pg_resetwal.sgml
+++ b/doc/src/sgml/ref/pg_resetwal.sgml
@@ -297,6 +297,26 @@ PostgreSQL documentation
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><option>-u <replaceable class="parameter">xid</replaceable></option></term>
+    <term><option>--oldest-transaction-id=<replaceable class="parameter">xid</replaceable></option></term>
+    <listitem>
+     <para>
+      Manually set the oldest unfrozen transaction ID.
+     </para>
+
+     <para>
+      A safe value can be determined by looking for the numerically smallest
+      file name in the directory <filename>pg_xact</filename> under the data directory
+      and then multiplying by 1048576 (0x100000).  Note that the file names are in
+      hexadecimal.  It is usually easiest to specify the option value in
+      hexadecimal too. For example, if <filename>0007</filename> is the smallest entry
+      in <filename>pg_xact</filename>, <literal>-u 0x700000</literal> will work (five
+      trailing zeroes provide the proper multiplier).
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><option>-x <replaceable class="parameter">xid</replaceable></option></term>
     <term><option>--next-transaction-id=<replaceable class="parameter">xid</replaceable></option></term>

diff --git a/src/bin/pg_resetwal/pg_resetwal.c b/src/bin/pg_resetwal/pg_resetwal.c
index 349347593cf0cfc485106d07c28eeddc0127dae4..200db99176337895329a9967d4cacc505bc94bb5 100644 (file)
--- a/src/bin/pg_resetwal/pg_resetwal.c
+++ b/src/bin/pg_resetwal/pg_resetwal.c
@@ -64,6 +64,7 @@ static XLogSegNo newXlogSegNo;    /* new XLOG segment # */
 static bool guessed = false;   /* T if we had to guess at any values */
 static const char *progname;
 static uint32 set_xid_epoch = (uint32) -1;
+static TransactionId set_oldest_xid = 0;
 static TransactionId set_xid = 0;
 static TransactionId set_oldest_commit_ts_xid = 0;
 static TransactionId set_newest_commit_ts_xid = 0;
@@ -101,6 +102,7 @@ main(int argc, char *argv[])
        {"dry-run", no_argument, NULL, 'n'},
        {"next-oid", required_argument, NULL, 'o'},
        {"multixact-offset", required_argument, NULL, 'O'},
+       {"oldest-transaction-id", required_argument, NULL, 'u'},
        {"next-transaction-id", required_argument, NULL, 'x'},
        {"wal-segsize", required_argument, NULL, 1},
        {NULL, 0, NULL, 0}
@@ -135,7 +137,7 @@ main(int argc, char *argv[])
    }
 
 
-   while ((c = getopt_long(argc, argv, "c:D:e:fl:m:no:O:x:", long_options, NULL)) != -1)
+   while ((c = getopt_long(argc, argv, "c:D:e:fl:m:no:O:u:x:", long_options, NULL)) != -1)
    {
        switch (c)
        {
@@ -168,6 +170,21 @@ main(int argc, char *argv[])
                }
                break;
 
+           case 'u':
+               set_oldest_xid = strtoul(optarg, &endptr, 0);
+               if (endptr == optarg || *endptr != '\0')
+               {
+                   pg_log_error("invalid argument for option %s", "-u");
+                   fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
+                   exit(1);
+               }
+               if (!TransactionIdIsNormal(set_oldest_xid))
+               {
+                   pg_log_error("oldest transaction ID (-u) must be greater or equal to %u", FirstNormalTransactionId);
+                   exit(1);
+               }
+               break;
+
            case 'x':
                set_xid = strtoul(optarg, &endptr, 0);
                if (endptr == optarg || *endptr != '\0')
@@ -176,9 +193,9 @@ main(int argc, char *argv[])
                    fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                    exit(1);
                }
-               if (set_xid == 0)
+               if (!TransactionIdIsNormal(set_xid))
                {
-                   pg_log_error("transaction ID (-x) must not be 0");
+                   pg_log_error("transaction ID (-x) must be greater or equal to %u", FirstNormalTransactionId);
                    exit(1);
                }
                break;
@@ -428,25 +445,17 @@ main(int argc, char *argv[])
            FullTransactionIdFromEpochAndXid(set_xid_epoch,
                                             XidFromFullTransactionId(ControlFile.checkPointCopy.nextFullXid));
 
-   if (set_xid != 0)
+   if (set_oldest_xid != 0)
    {
+       ControlFile.checkPointCopy.oldestXid = set_oldest_xid;
+       ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
+   }
+
+   if (set_xid != 0)
        ControlFile.checkPointCopy.nextFullXid =
            FullTransactionIdFromEpochAndXid(EpochFromFullTransactionId(ControlFile.checkPointCopy.nextFullXid),
                                             set_xid);
 
-       /*
-        * For the moment, just set oldestXid to a value that will force
-        * immediate autovacuum-for-wraparound.  It's not clear whether adding
-        * user control of this is useful, so let's just do something that's
-        * reasonably safe.  The magic constant here corresponds to the
-        * maximum allowed value of autovacuum_freeze_max_age.
-        */
-       ControlFile.checkPointCopy.oldestXid = set_xid - 2000000000;
-       if (ControlFile.checkPointCopy.oldestXid < FirstNormalTransactionId)
-           ControlFile.checkPointCopy.oldestXid += FirstNormalTransactionId;
-       ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
-   }
-
    if (set_oldest_commit_ts_xid != 0)
        ControlFile.checkPointCopy.oldestCommitTsXid = set_oldest_commit_ts_xid;
    if (set_newest_commit_ts_xid != 0)
@@ -1228,19 +1237,20 @@ usage(void)
    printf(_("Usage:\n  %s [OPTION]... DATADIR\n\n"), progname);
    printf(_("Options:\n"));
    printf(_("  -c, --commit-timestamp-ids=XID,XID\n"
-            "                                 set oldest and newest transactions bearing\n"
-            "                                 commit timestamp (zero means no change)\n"));
-   printf(_(" [-D, --pgdata=]DATADIR          data directory\n"));
-   printf(_("  -e, --epoch=XIDEPOCH           set next transaction ID epoch\n"));
-   printf(_("  -f, --force                    force update to be done\n"));
-   printf(_("  -l, --next-wal-file=WALFILE    set minimum starting location for new WAL\n"));
-   printf(_("  -m, --multixact-ids=MXID,MXID  set next and oldest multitransaction ID\n"));
-   printf(_("  -n, --dry-run                  no update, just show what would be done\n"));
-   printf(_("  -o, --next-oid=OID             set next OID\n"));
-   printf(_("  -O, --multixact-offset=OFFSET  set next multitransaction offset\n"));
-   printf(_("  -V, --version                  output version information, then exit\n"));
-   printf(_("  -x, --next-transaction-id=XID  set next transaction ID\n"));
-   printf(_("      --wal-segsize=SIZE         size of WAL segments, in megabytes\n"));
-   printf(_("  -?, --help                     show this help, then exit\n"));
+            "                                   set oldest and newest transactions bearing\n"
+            "                                   commit timestamp (zero means no change)\n"));
+   printf(_(" [-D, --pgdata=]DATADIR            data directory\n"));
+   printf(_("  -e, --epoch=XIDEPOCH             set next transaction ID epoch\n"));
+   printf(_("  -f, --force                      force update to be done\n"));
+   printf(_("  -l, --next-wal-file=WALFILE      set minimum starting location for new WAL\n"));
+   printf(_("  -m, --multixact-ids=MXID,MXID    set next and oldest multitransaction ID\n"));
+   printf(_("  -n, --dry-run                    no update, just show what would be done\n"));
+   printf(_("  -o, --next-oid=OID               set next OID\n"));
+   printf(_("  -O, --multixact-offset=OFFSET    set next multitransaction offset\n"));
+   printf(_("  -u, --oldest-transaction-id=XID  set oldest transaction ID\n"));
+   printf(_("  -V, --version                    output version information, then exit\n"));
+   printf(_("  -x, --next-transaction-id=XID    set next transaction ID\n"));
+   printf(_("      --wal-segsize=SIZE           size of WAL segments, in megabytes\n"));
+   printf(_("  -?, --help                       show this help, then exit\n"));
    printf(_("\nReport bugs to <pgsql-bugs@lists.postgresql.org>.\n"));
 }

diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index 298ae50757c13d390eb635eb4c381f034dbb2c01..1b68e3e872ddb700165db59fc0ee35543a237469 100644 (file)
--- a/src/bin/pg_upgrade/controldata.c
+++ b/src/bin/pg_upgrade/controldata.c
@@ -44,6 +44,7 @@ get_control_data(ClusterInfo *cluster, bool live_check)
    bool        got_oid = false;
    bool        got_multi = false;
    bool        got_oldestmulti = false;
+   bool        got_oldestxid = false;
    bool        got_mxoff = false;
    bool        got_nextxlogfile = false;
    bool        got_float8_pass_by_value = false;
@@ -312,6 +313,17 @@ get_control_data(ClusterInfo *cluster, bool live_check)
            cluster->controldata.chkpnt_nxtmulti = str2uint(p);
            got_multi = true;
        }
+       else if ((p = strstr(bufin, "Latest checkpoint's oldestXID:")) != NULL)
+       {
+           p = strchr(p, ':');
+
+           if (p == NULL || strlen(p) <= 1)
+               pg_fatal("%d: controldata retrieval problem\n", __LINE__);
+
+           p++;                /* remove ':' char */
+           cluster->controldata.chkpnt_oldstxid = str2uint(p);
+           got_oldestxid = true;
+       }
        else if ((p = strstr(bufin, "Latest checkpoint's oldestMultiXid:")) != NULL)
        {
            p = strchr(p, ':');
@@ -530,7 +542,7 @@ get_control_data(ClusterInfo *cluster, bool live_check)
 
    /* verify that we got all the mandatory pg_control data */
    if (!got_xid || !got_oid ||
-       !got_multi ||
+       !got_multi || !got_oldestxid ||
        (!got_oldestmulti &&
         cluster->controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER) ||
        !got_mxoff || (!live_check && !got_nextxlogfile) ||
@@ -561,6 +573,9 @@ get_control_data(ClusterInfo *cluster, bool live_check)
            cluster->controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
            pg_log(PG_REPORT, "  latest checkpoint oldest MultiXactId\n");
 
+       if (!got_oldestxid)
+           pg_log(PG_REPORT, "  latest checkpoint oldestXID\n");
+
        if (!got_mxoff)
            pg_log(PG_REPORT, "  latest checkpoint next MultiXactOffset\n");
 

diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index cb0aff3e33a15138992cec76abdc1c0ac2f95cc7..3d7b21526bcbed1d6c576ad6fd2ef4dd8a7d40b6 100644 (file)
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -470,6 +470,13 @@ copy_xact_xlog_xid(void)
                      GET_MAJOR_VERSION(new_cluster.major_version) <= 906 ?
                      "pg_clog" : "pg_xact");
 
+   prep_status("Setting oldest XID for new cluster");
+   exec_prog(UTILITY_LOG_FILE, NULL, true, true,
+             "\"%s/pg_resetwal\" -f -u %u \"%s\"",
+             new_cluster.bindir, old_cluster.controldata.chkpnt_oldstxid,
+             new_cluster.pgdata);
+   check_ok();
+
    /* set the next transaction id and epoch of the new cluster */
    prep_status("Setting next transaction ID and epoch for new cluster");
    exec_prog(UTILITY_LOG_FILE, NULL, true, true,

diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index 0a1712ba589d794cac4e12d54c6072ccbb14be71..1e43ede206af49d5b95e77f341bea5854fc88dfe 100644 (file)
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -215,6 +215,7 @@ typedef struct
    uint32      chkpnt_nxtmulti;
    uint32      chkpnt_nxtmxoff;
    uint32      chkpnt_oldstMulti;
+   uint32      chkpnt_oldstxid;
    uint32      align;
    uint32      blocksz;
    uint32      largesz;