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[email protected], 87da83168c644fd9aae38f546cc70295@opammb0562.comp.optiver.com

Author: Bertrand Drouvot

Backpatch-through: 9.6

diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index 9758fa652a2ffdfaf20750d251b936ddcea3ffca..7a87350d7d46209a9275b7c915da075b006aa595 100644 (file)
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -247,6 +247,25 @@ PostgreSQL documentation
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><option>-u <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</option> <replaceable class="parameter">xid</replaceable></term>
     <listitem>

diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c
index 3e79482ca22dfc43cca0c5714f8731f3c3562657..71f2391925db362aa8254646a57064da694e7691 100644 (file)
--- a/src/bin/pg_resetxlog/pg_resetxlog.c
+++ b/src/bin/pg_resetxlog/pg_resetxlog.c
@@ -63,6 +63,7 @@ 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;
@@ -116,7 +117,7 @@ main(int argc, char *argv[])
    }
 
 
-   while ((c = getopt(argc, argv, "c:D:e:fl:m:no:O:x:")) != -1)
+   while ((c = getopt(argc, argv, "c:D:e:fl:m:no:O:u:x:")) != -1)
    {
        switch (c)
        {
@@ -149,6 +150,21 @@ main(int argc, char *argv[])
                }
                break;
 
+           case 'u':
+               set_oldest_xid = strtoul(optarg, &endptr, 0);
+               if (endptr == optarg || *endptr != '\0')
+               {
+                   fprintf(stderr, _("invalid argument for option %s"), "-u");
+                   fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
+                   exit(1);
+               }
+               if (!TransactionIdIsNormal(set_oldest_xid))
+               {
+                   fprintf(stderr, _("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')
@@ -370,23 +386,15 @@ main(int argc, char *argv[])
    if (set_xid_epoch != -1)
        ControlFile.checkPointCopy.nextXidEpoch = set_xid_epoch;
 
-   if (set_xid != 0)
+   if (set_oldest_xid != 0)
    {
-       ControlFile.checkPointCopy.nextXid = 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.oldestXid = set_oldest_xid;
        ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
    }
 
+   if (set_xid != 0)
+       ControlFile.checkPointCopy.nextXid = set_xid;
+
    if (set_oldest_commit_ts_xid != 0)
        ControlFile.checkPointCopy.oldestCommitTsXid = set_oldest_commit_ts_xid;
    if (set_newest_commit_ts_xid != 0)
@@ -1243,6 +1251,7 @@ usage(void)
    printf(_("  -n               no update, just show what would be done (for testing)\n"));
    printf(_("  -o OID           set next OID\n"));
    printf(_("  -O OFFSET        set next multitransaction offset\n"));
+   printf(_("  -u XID           set oldest transaction ID\n"));
    printf(_("  -V, --version    output version information, then exit\n"));
    printf(_("  -x XID           set next transaction ID\n"));
    printf(_("  -?, --help       show this help, then exit\n"));

diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index 2f7ba40dc9834d47c8913b17f6fe7a60f328e4f2..817777793982193d6b648dcaadab412354d77719 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;
@@ -306,6 +307,17 @@ 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, ':');
@@ -524,7 +536,7 @@ 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) ||
@@ -552,6 +564,9 @@ 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 02078c0357341db65e7510af5dac26e0ebf90942..8bbb86630c8dce04d62b8a26c0a148342ecddf80 100644 (file)
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -408,6 +408,13 @@ copy_clog_xlog_xid(void)
    /* copy old commit logs to new data dir */
    copy_subdir_files("pg_clog");
 
+   prep_status("Setting oldest XID for new cluster");
+   exec_prog(UTILITY_LOG_FILE, NULL, true,
+             "\"%s/pg_resetxlog\" -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,

diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index d4f6e0fe085f1de0f178159bb6cf0fe2250c7020..a7f6e4920e81e3da5c57402d9f434bdbd65f8e5e 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;