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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
This commit is contained in:
Bruce Momjian 2021-07-26 22:38:15 -04:00
parent 24ba1a87e4
commit 74cf7d46a9
5 changed files with 85 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
doc/src/sgml/ref/pg_resetwal.sgml
View File

@ -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>

72
src/bin/pg_resetwal/pg_resetwal.c
View File

@ -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.nextXid));
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.nextXid =
FullTransactionIdFromEpochAndXid(EpochFromFullTransactionId(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.oldestXidDB = InvalidOid;
}
if (set_oldest_commit_ts_xid != 0)
ControlFile.checkPointCopy.oldestCommitTsXid = set_oldest_commit_ts_xid;
if (set_newest_commit_ts_xid != 0)
@ -1209,20 +1218,21 @@ 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 <%s>.\n"), PACKAGE_BUGREPORT);
printf(_("%s home page: <%s>\n"), PACKAGE_NAME, PACKAGE_URL);
}

17
src/bin/pg_upgrade/controldata.c
View File

@ -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, ':');
@ -544,7 +556,7 @@ 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) ||
@ -575,6 +587,9 @@ 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");

7
src/bin/pg_upgrade/pg_upgrade.c
View File

@ -467,6 +467,13 @@ 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,

1
src/bin/pg_upgrade/pg_upgrade.h
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@ -207,6 +207,7 @@ typedef struct
uint32 chkpnt_nxtmulti;
uint32 chkpnt_nxtmxoff;
uint32 chkpnt_oldstMulti;
uint32 chkpnt_oldstxid;
uint32 align;
uint32 blocksz;
uint32 largesz;