Add --min-xid-age and --min-mxid-age options to vacuumdb

These two new options can be used to improve the selectivity of
relations to vacuum or analyze even further depending on the age of
respectively their transaction ID or multixact ID, so as it is possible
to prioritize tables to prevent wraparound of one or the other.
Combined with --table, it is possible to target a subset of tables to
choose as potential processing targets.

Author: Nathan Bossart
Reviewed-by: Michael Paquier, Masahiko Sawada
Discussion: https://postgr.es/m/FFE5373C-E26A-495B-B5C8-911EC4A41C5E@amazon.com

doc/src/sgml/ref/vacuumdb.sgml

@@ -172,6 +172,60 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>--min-mxid-age <replaceable class="parameter">mxid_age</replaceable></option></term>
+      <listitem>
+       <para>
+        Only execute the vacuum or analyze commands on tables with a multixact
+        ID age of at least <replaceable class="parameter">mxid_age</replaceable>.
+        This setting is useful for prioritizing tables to process to prevent
+        multixact ID wraparound (see
+        <xref linkend="vacuum-for-multixact-wraparound"/>).
+       </para>
+       <para>
+        For the purposes of this option, the multixact ID age of a relation is
+        the greatest of the ages of the main relation and its associated
+        <acronym>TOAST</acronym> table, if one exists.  Since the commands
+        issued by <application>vacuumdb</application> will also process the
+        <acronym>TOAST</acronym> table for the relation if necessary, it does
+        not need to be considered separately.
+       </para>
+       <note>
+        <para>
+         This option is only available for servers running
+         <productname>PostgreSQL</productname> 9.6 and later.
+        </para>
+       </note>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>--min-xid-age <replaceable class="parameter">xid_age</replaceable></option></term>
+      <listitem>
+       <para>
+        Only execute the vacuum or analyze commands on tables with a
+        transaction ID age of at least
+        <replaceable class="parameter">xid_age</replaceable>.  This setting
+        is useful for prioritizing tables to process to prevent transaction
+        ID wraparound (see <xref linkend="vacuum-for-wraparound"/>).
+       </para>
+       <para>
+        For the purposes of this option, the transaction ID age of a relation
+        is the greatest of the ages of the main relation and its associated
+        <acronym>TOAST</acronym> table, if one exists.  Since the commands
+        issued by <application>vacuumdb</application> will also process the
+        <acronym>TOAST</acronym> table for the relation if necessary, it does
+        not need to be considered separately.
+       </para>
+       <note>
+        <para>
+         This option is only available for servers running
+         <productname>PostgreSQL</productname> 9.6 and later.
+        </para>
+       </note>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><option>-q</option></term>
       <term><option>--quiet</option></term>

src/bin/scripts/t/100_vacuumdb.pl

@@ -3,7 +3,7 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 38;
+use Test::More tests => 44;
 
 program_help_ok('vacuumdb');
 program_version_ok('vacuumdb');
@@ -95,3 +95,20 @@ $node->command_checks_all(
 	[qr/^.*vacuuming database "postgres"/],
 	[qr/^WARNING.*cannot vacuum non-tables or special system tables/s],
 	'vacuumdb with view');
+$node->command_fails(
+	[ 'vacuumdb', '--table', 'vactable', '--min-mxid-age', '0',
+	  'postgres'],
+	'vacuumdb --min-mxid-age with incorrect value');
+$node->command_fails(
+	[ 'vacuumdb', '--table', 'vactable', '--min-xid-age', '0',
+	  'postgres'],
+	'vacuumdb --min-xid-age with incorrect value');
+$node->issues_sql_like(
+	[ 'vacuumdb', '--table', 'vactable', '--min-mxid-age', '2147483000',
+	  'postgres'],
+	qr/GREATEST.*relminmxid.*2147483000/,
+	'vacuumdb --table --min-mxid-age');
+$node->issues_sql_like(
+	[ 'vacuumdb', '--min-xid-age', '2147483001', 'postgres' ],
+	qr/GREATEST.*relfrozenxid.*2147483001/,
+	'vacuumdb --table --min-xid-age');

src/bin/scripts/vacuumdb.c

@@ -43,6 +43,8 @@ typedef struct vacuumingOptions
 	bool		freeze;
 	bool		disable_page_skipping;
 	bool		skip_locked;
+	int			min_xid_age;
+	int			min_mxid_age;
 } vacuumingOptions;
 
 
@@ -113,6 +115,8 @@ main(int argc, char *argv[])
 		{"analyze-in-stages", no_argument, NULL, 3},
 		{"disable-page-skipping", no_argument, NULL, 4},
 		{"skip-locked", no_argument, NULL, 5},
+		{"min-xid-age", required_argument, NULL, 6},
+		{"min-mxid-age", required_argument, NULL, 7},
 		{NULL, 0, NULL, 0}
 	};
 
@@ -222,6 +226,24 @@ main(int argc, char *argv[])
 			case 5:
 				vacopts.skip_locked = true;
 				break;
+			case 6:
+				vacopts.min_xid_age = atoi(optarg);
+				if (vacopts.min_xid_age <= 0)
+				{
+					fprintf(stderr, _("%s: minimum transaction ID age must be at least 1\n"),
+							progname);
+					exit(1);
+				}
+				break;
+			case 7:
+				vacopts.min_mxid_age = atoi(optarg);
+				if (vacopts.min_mxid_age <= 0)
+				{
+					fprintf(stderr, _("%s: minimum multixact ID age must be at least 1\n"),
+							progname);
+					exit(1);
+				}
+				break;
 			default:
 				fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
 				exit(1);
@@ -370,6 +392,7 @@ vacuum_one_database(const char *dbname, vacuumingOptions *vacopts,
 	bool		failed = false;
 	bool		parallel = concurrentCons > 1;
 	bool		tables_listed = false;
+	bool		has_where = false;
 	const char *stage_commands[] = {
 		"SET default_statistics_target=1; SET vacuum_cost_delay=0;",
 		"SET default_statistics_target=10; RESET vacuum_cost_delay;",
@@ -403,6 +426,20 @@ vacuum_one_database(const char *dbname, vacuumingOptions *vacopts,
 		exit(1);
 	}
 
+	if (vacopts->min_xid_age != 0 && PQserverVersion(conn) < 90600)
+	{
+		fprintf(stderr, _("%s: cannot use the \"%s\" option on server versions older than PostgreSQL 9.6\n"),
+				progname, "--min-xid-age");
+		exit(1);
+	}
+
+	if (vacopts->min_mxid_age != 0 && PQserverVersion(conn) < 90600)
+	{
+		fprintf(stderr, _("%s: cannot use the \"%s\" option on server versions older than PostgreSQL 9.6\n"),
+				progname, "--min-mxid-age");
+		exit(1);
+	}
+
 	if (!quiet)
 	{
 		if (stage != ANALYZE_NO_STAGE)
@@ -477,7 +514,9 @@ vacuum_one_database(const char *dbname, vacuumingOptions *vacopts,
 	appendPQExpBuffer(&catalog_query,
 					  " FROM pg_catalog.pg_class c\n"
 					  " JOIN pg_catalog.pg_namespace ns"
-					  " ON c.relnamespace OPERATOR(pg_catalog.=) ns.oid\n");
+					  " ON c.relnamespace OPERATOR(pg_catalog.=) ns.oid\n"
+					  " LEFT JOIN pg_catalog.pg_class t"
+					  " ON c.reltoastrelid OPERATOR(pg_catalog.=) t.oid\n");
 
 	/* Used to match the tables listed by the user */
 	if (tables_listed)
@@ -491,9 +530,43 @@ vacuum_one_database(const char *dbname, vacuumingOptions *vacopts,
 	 * processed in which case the user will know about it.
 	 */
 	if (!tables_listed)
+	{
 		appendPQExpBuffer(&catalog_query, " WHERE c.relkind OPERATOR(pg_catalog.=) ANY (array["
 						  CppAsString2(RELKIND_RELATION) ", "
 						  CppAsString2(RELKIND_MATVIEW) "])\n");
+		has_where = true;
+	}
+
+	/*
+	 * For --min-xid-age and --min-mxid-age, the age of the relation is the
+	 * greatest of the ages of the main relation and its associated TOAST
+	 * table.  The commands generated by vacuumdb will also process the TOAST
+	 * table for the relation if necessary, so it does not need to be
+	 * considered separately.
+	 */
+	if (vacopts->min_xid_age != 0)
+	{
+		appendPQExpBuffer(&catalog_query,
+						  " %s GREATEST(pg_catalog.age(c.relfrozenxid),"
+						  " pg_catalog.age(t.relfrozenxid)) "
+						  " OPERATOR(pg_catalog.>=) '%d'::pg_catalog.int4\n"
+						  " AND c.relfrozenxid OPERATOR(pg_catalog.!=)"
+						  " '0'::pg_catalog.xid\n",
+						  has_where ? "AND" : "WHERE", vacopts->min_xid_age);
+		has_where = true;
+	}
+
+	if (vacopts->min_mxid_age != 0)
+	{
+		appendPQExpBuffer(&catalog_query,
+						  " %s GREATEST(pg_catalog.mxid_age(c.relminmxid),"
+						  " pg_catalog.mxid_age(t.relminmxid)) OPERATOR(pg_catalog.>=)"
+						  " '%d'::pg_catalog.int4\n"
+						  " AND c.relminmxid OPERATOR(pg_catalog.!=)"
+						  " '0'::pg_catalog.xid\n",
+						  has_where ? "AND" : "WHERE", vacopts->min_mxid_age);
+		has_where = true;
+	}
 
 	/*
 	 * Execute the catalog query.  We use the default search_path for this
@@ -1152,6 +1225,8 @@ help(const char *progname)
 	printf(_("  -f, --full                      do full vacuuming\n"));
 	printf(_("  -F, --freeze                    freeze row transaction information\n"));
 	printf(_("  -j, --jobs=NUM                  use this many concurrent connections to vacuum\n"));
+	printf(_("      --min-mxid-age=MXID_AGE     minimum multixact ID age of tables to vacuum\n"));
+	printf(_("      --min-xid-age=XID_AGE       minimum transaction ID age of tables to vacuum\n"));
 	printf(_("  -q, --quiet                     don't write any messages\n"));
 	printf(_("      --skip-locked               skip relations that cannot be immediately locked\n"));
 	printf(_("  -t, --table='TABLE[(COLUMNS)]'  vacuum specific table(s) only\n"));