Introduce xid8-based functions to replace txid_XXX.

The txid_XXX family of fmgr functions exposes 64 bit transaction IDs to
users as int8.  Now that we have an SQL type xid8 for FullTransactionId,
define a new set of functions including pg_current_xact_id() and
pg_current_snapshot() based on that.  Keep the old functions around too,
for now.

It's a bit sneaky to use the same C functions for both, but since the
binary representation is identical except for the signedness of the
type, and since older functions are the ones using the wrong signedness,
and since we'll presumably drop the older ones after a reasonable period
of time, it seems reasonable to switch to FullTransactionId internally
and share the code for both.

Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: Takao Fujii <btfujiitkp@oss.nttdata.com>
Reviewed-by: Yoshikazu Imai <imai.yoshikazu@fujitsu.com>
Reviewed-by: Mark Dilger <mark.dilger@enterprisedb.com>
Discussion: https://postgr.es/m/20190725000636.666m5mad25wfbrri%40alap3.anarazel.de

16 files changed, 473 insertions, 36 deletions

diff --git a/src/test/modules/commit_ts/t/004_restart.pl b/src/test/modules/commit_ts/t/004_restart.pl
index bd4b943305..39ca25a06b 100644
--- a/src/test/modules/commit_ts/t/004_restart.pl
+++ b/src/test/modules/commit_ts/t/004_restart.pl
@@ -45,7 +45,7 @@ my $xid = $node_master->safe_psql(
 	'postgres', qq[
 	BEGIN;
 	INSERT INTO committs_test(x, y) VALUES (1, current_timestamp);
-	SELECT txid_current();
+	SELECT pg_current_xact_id()::xid;
 	COMMIT;
 ]);
 
@@ -93,7 +93,7 @@ DECLARE
     i int;
     BEGIN
         FOR i in 1..cnt LOOP
-            EXECUTE 'SELECT txid_current()';
+            EXECUTE 'SELECT pg_current_xact_id()';
             COMMIT;
         END LOOP;
     END;
@@ -115,7 +115,7 @@ my $xid_disabled = $node_master->safe_psql(
 	'postgres', qq[
 	BEGIN;
 	INSERT INTO committs_test(x, y) VALUES (2, current_timestamp);
-	SELECT txid_current();
+	SELECT pg_current_xact_id();
 	COMMIT;
 ]);
 
diff --git a/src/test/modules/test_ddl_deparse/expected/create_table.out b/src/test/modules/test_ddl_deparse/expected/create_table.out
index 523c996093..c7c9bf8971 100644
--- a/src/test/modules/test_ddl_deparse/expected/create_table.out
+++ b/src/test/modules/test_ddl_deparse/expected/create_table.out
@@ -43,7 +43,7 @@ CREATE TABLE datatype_table (
     v_json         JSON,
     v_xml          XML,
     v_uuid         UUID,
-    v_txid_snapshot txid_snapshot,
+    v_pg_snapshot  pg_snapshot,
     v_enum         ENUM_TEST,
     v_postal_code  japanese_postal_code,
     v_int2range    int2range,
diff --git a/src/test/modules/test_ddl_deparse/sql/create_table.sql b/src/test/modules/test_ddl_deparse/sql/create_table.sql
index dd3a908638..39cdb9df03 100644
--- a/src/test/modules/test_ddl_deparse/sql/create_table.sql
+++ b/src/test/modules/test_ddl_deparse/sql/create_table.sql
@@ -44,7 +44,7 @@ CREATE TABLE datatype_table (
     v_json         JSON,
     v_xml          XML,
     v_uuid         UUID,
-    v_txid_snapshot txid_snapshot,
+    v_pg_snapshot  pg_snapshot,
     v_enum         ENUM_TEST,
     v_postal_code  japanese_postal_code,
     v_int2range    int2range,
diff --git a/src/test/recovery/t/003_recovery_targets.pl b/src/test/recovery/t/003_recovery_targets.pl
index fd14bab208..2a520e6db1 100644
--- a/src/test/recovery/t/003_recovery_targets.pl
+++ b/src/test/recovery/t/003_recovery_targets.pl
@@ -68,7 +68,7 @@ $node_master->backup('my_backup');
 $node_master->safe_psql('postgres',
 	"INSERT INTO tab_int VALUES (generate_series(1001,2000))");
 my $ret = $node_master->safe_psql('postgres',
-	"SELECT pg_current_wal_lsn(), txid_current();");
+	"SELECT pg_current_wal_lsn(), pg_current_xact_id();");
 my ($lsn2, $recovery_txid) = split /\|/, $ret;
 
 # More data, with recovery target timestamp
diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index 526a3481fb..ca6e92b50d 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -24,7 +24,7 @@ $node->start;
 
 my ($stdin, $stdout, $stderr) = ('', '', '');
 
-# Ensure that txid_status reports 'aborted' for xacts
+# Ensure that pg_xact_status reports 'aborted' for xacts
 # that were in-progress during crash. To do that, we need
 # an xact to be in-progress when we crash and we need to know
 # its xid.
@@ -42,7 +42,7 @@ my $tx = IPC::Run::start(
 $stdin .= q[
 BEGIN;
 CREATE TABLE mine(x integer);
-SELECT txid_current();
+SELECT pg_current_xact_id();
 ];
 $tx->pump until $stdout =~ /[[:digit:]]+[\r\n]$/;
 
@@ -50,7 +50,7 @@ $tx->pump until $stdout =~ /[[:digit:]]+[\r\n]$/;
 my $xid = $stdout;
 chomp($xid);
 
-is($node->safe_psql('postgres', qq[SELECT txid_status('$xid');]),
+is($node->safe_psql('postgres', qq[SELECT pg_xact_status('$xid');]),
 	'in progress', 'own xid is in-progress');
 
 # Crash and restart the postmaster
@@ -58,11 +58,11 @@ $node->stop('immediate');
 $node->start;
 
 # Make sure we really got a new xid
-cmp_ok($node->safe_psql('postgres', 'SELECT txid_current()'),
+cmp_ok($node->safe_psql('postgres', 'SELECT pg_current_xact_id()'),
 	'>', $xid, 'new xid after restart is greater');
 
 # and make sure we show the in-progress xact as aborted
-is($node->safe_psql('postgres', qq[SELECT txid_status('$xid');]),
+is($node->safe_psql('postgres', qq[SELECT pg_xact_status('$xid');]),
 	'aborted', 'xid is aborted after crash');
 
 $tx->kill_kill;
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index e46775afbf..f343f9b42e 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -2556,7 +2556,7 @@ from pg_locks l join pg_class c on l.relation = c.oid
 where virtualtransaction = (
         select virtualtransaction
         from pg_locks
-        where transactionid = txid_current()::integer)
+        where transactionid = pg_current_xact_id()::xid)
 and locktype = 'relation'
 and relnamespace != (select oid from pg_namespace where nspname = 'pg_catalog')
 and c.relname != 'my_locks'
@@ -2719,7 +2719,7 @@ from pg_locks l join pg_class c on l.relation = c.oid
 where virtualtransaction = (
         select virtualtransaction
         from pg_locks
-        where transactionid = txid_current()::integer)
+        where transactionid = pg_current_xact_id()::xid)
 and locktype = 'relation'
 and relnamespace != (select oid from pg_namespace where nspname = 'pg_catalog')
 and c.relname = 'my_locks'
diff --git a/src/test/regress/expected/hs_standby_functions.out b/src/test/regress/expected/hs_standby_functions.out
index e0af677ea1..ce846b758b 100644
--- a/src/test/regress/expected/hs_standby_functions.out
+++ b/src/test/regress/expected/hs_standby_functions.out
@@ -4,9 +4,9 @@
 -- hs_standby_functions.sql
 --
 -- should fail
-select txid_current();
-ERROR:  cannot execute txid_current() during recovery
-select length(txid_current_snapshot()::text) >= 4;
+select pg_current_xact_id();
+ERROR:  cannot execute pg_current_xact_id() during recovery
+select length(pg_current_snapshot()::text) >= 4;
  ?column? 
 ----------
  t
diff --git a/src/test/regress/expected/opr_sanity.out b/src/test/regress/expected/opr_sanity.out
index 0c03afe53d..8d350ab61b 100644
--- a/src/test/regress/expected/opr_sanity.out
+++ b/src/test/regress/expected/opr_sanity.out
@@ -194,9 +194,11 @@ WHERE p1.oid != p2.oid AND
 ORDER BY 1, 2;
  prorettype | prorettype 
 ------------+------------
+         20 |       9419
          25 |       1043
        1114 |       1184
-(2 rows)
+       2970 |       8355
+(4 rows)
 
 SELECT DISTINCT p1.proargtypes[0], p2.proargtypes[0]
 FROM pg_proc AS p1, pg_proc AS p2
@@ -210,11 +212,13 @@ WHERE p1.oid != p2.oid AND
 ORDER BY 1, 2;
  proargtypes | proargtypes 
 -------------+-------------
+          20 |        9419
           25 |        1042
           25 |        1043
         1114 |        1184
         1560 |        1562
-(4 rows)
+        2970 |        8355
+(6 rows)
 
 SELECT DISTINCT p1.proargtypes[1], p2.proargtypes[1]
 FROM pg_proc AS p1, pg_proc AS p2
@@ -231,7 +235,8 @@ ORDER BY 1, 2;
           23 |          28
         1114 |        1184
         1560 |        1562
-(3 rows)
+        2970 |        8355
+(4 rows)
 
 SELECT DISTINCT p1.proargtypes[2], p2.proargtypes[2]
 FROM pg_proc AS p1, pg_proc AS p2
diff --git a/src/test/regress/expected/txid.out b/src/test/regress/expected/txid.out
index 015dae3051..95ba66e95e 100644
--- a/src/test/regress/expected/txid.out
+++ b/src/test/regress/expected/txid.out
@@ -1,4 +1,7 @@
 -- txid_snapshot data type and related functions
+-- Note: these are backward-compatibility functions and types, and have been
+-- replaced by new xid8-based variants.  See xid.sql.  The txid variants will
+-- be removed in a future release.
 -- i/o
 select '12:13:'::txid_snapshot;
  txid_snapshot 
@@ -20,19 +23,19 @@ select '12:16:14,14'::txid_snapshot;
 
 -- errors
 select '31:12:'::txid_snapshot;
-ERROR:  invalid input syntax for type txid_snapshot: "31:12:"
+ERROR:  invalid input syntax for type pg_snapshot: "31:12:"
 LINE 1: select '31:12:'::txid_snapshot;
                ^
 select '0:1:'::txid_snapshot;
-ERROR:  invalid input syntax for type txid_snapshot: "0:1:"
+ERROR:  invalid input syntax for type pg_snapshot: "0:1:"
 LINE 1: select '0:1:'::txid_snapshot;
                ^
 select '12:13:0'::txid_snapshot;
-ERROR:  invalid input syntax for type txid_snapshot: "12:13:0"
+ERROR:  invalid input syntax for type pg_snapshot: "12:13:0"
 LINE 1: select '12:13:0'::txid_snapshot;
                ^
 select '12:16:14,13'::txid_snapshot;
-ERROR:  invalid input syntax for type txid_snapshot: "12:16:14,13"
+ERROR:  invalid input syntax for type pg_snapshot: "12:16:14,13"
 LINE 1: select '12:16:14,13'::txid_snapshot;
                ^
 create temp table snapshot_test (
@@ -235,7 +238,7 @@ SELECT txid_snapshot '1:9223372036854775807:3';
 (1 row)
 
 SELECT txid_snapshot '1:9223372036854775808:3';
-ERROR:  invalid input syntax for type txid_snapshot: "1:9223372036854775808:3"
+ERROR:  invalid input syntax for type pg_snapshot: "1:9223372036854775808:3"
 LINE 1: SELECT txid_snapshot '1:9223372036854775808:3';
                              ^
 -- test txid_current_if_assigned
diff --git a/src/test/regress/expected/update.out b/src/test/regress/expected/update.out
index b7f90de52b..bf939d79f6 100644
--- a/src/test/regress/expected/update.out
+++ b/src/test/regress/expected/update.out
@@ -230,10 +230,9 @@ INSERT INTO upsert_test VALUES (1, 'Bat') ON CONFLICT(a)
 -- ON CONFLICT using system attributes in RETURNING, testing both the
 -- inserting and updating paths. See bug report at:
 -- https://www.postgresql.org/message-id/73436355-6432-49B1-92ED-1FE4F7E7E100%40finefun.com.au
-CREATE FUNCTION xid_current() RETURNS xid LANGUAGE SQL AS $$SELECT (txid_current() % ((1::int8<<32)))::text::xid;$$;
 INSERT INTO upsert_test VALUES (2, 'Beeble') ON CONFLICT(a)
   DO UPDATE SET (b, a) = (SELECT b || ', Excluded', a from upsert_test i WHERE i.a = excluded.a)
-  RETURNING tableoid::regclass, xmin = xid_current() AS xmin_correct, xmax = 0 AS xmax_correct;
+  RETURNING tableoid::regclass, xmin = pg_current_xact_id()::xid AS xmin_correct, xmax = 0 AS xmax_correct;
   tableoid   | xmin_correct | xmax_correct 
 -------------+--------------+--------------
  upsert_test | t            | t
@@ -243,13 +242,12 @@ INSERT INTO upsert_test VALUES (2, 'Beeble') ON CONFLICT(a)
 -- but it seems worthwhile to have to be explicit if that changes.
 INSERT INTO upsert_test VALUES (2, 'Brox') ON CONFLICT(a)
   DO UPDATE SET (b, a) = (SELECT b || ', Excluded', a from upsert_test i WHERE i.a = excluded.a)
-  RETURNING tableoid::regclass, xmin = xid_current() AS xmin_correct, xmax = xid_current() AS xmax_correct;
+  RETURNING tableoid::regclass, xmin = pg_current_xact_id()::xid AS xmin_correct, xmax = pg_current_xact_id()::xid AS xmax_correct;
   tableoid   | xmin_correct | xmax_correct 
 -------------+--------------+--------------
  upsert_test | t            | t
 (1 row)
 
-DROP FUNCTION xid_current();
 DROP TABLE update_test;
 DROP TABLE upsert_test;
 ---------------------------
diff --git a/src/test/regress/expected/xid.out b/src/test/regress/expected/xid.out
index e9e1fa8259..b7a1ed0f9e 100644
--- a/src/test/regress/expected/xid.out
+++ b/src/test/regress/expected/xid.out
@@ -134,3 +134,329 @@ create table xid8_t1 (x xid8);
 create index on xid8_t1 using btree(x);
 create index on xid8_t1 using hash(x);
 drop table xid8_t1;
+-- pg_snapshot data type and related functions
+-- Note: another set of tests similar to this exists in txid.sql, for a limited
+-- time (the relevant functions share C code)
+-- i/o
+select '12:13:'::pg_snapshot;
+ pg_snapshot 
+-------------
+ 12:13:
+(1 row)
+
+select '12:18:14,16'::pg_snapshot;
+ pg_snapshot 
+-------------
+ 12:18:14,16
+(1 row)
+
+select '12:16:14,14'::pg_snapshot;
+ pg_snapshot 
+-------------
+ 12:16:14
+(1 row)
+
+-- errors
+select '31:12:'::pg_snapshot;
+ERROR:  invalid input syntax for type pg_snapshot: "31:12:"
+LINE 1: select '31:12:'::pg_snapshot;
+               ^
+select '0:1:'::pg_snapshot;
+ERROR:  invalid input syntax for type pg_snapshot: "0:1:"
+LINE 1: select '0:1:'::pg_snapshot;
+               ^
+select '12:13:0'::pg_snapshot;
+ERROR:  invalid input syntax for type pg_snapshot: "12:13:0"
+LINE 1: select '12:13:0'::pg_snapshot;
+               ^
+select '12:16:14,13'::pg_snapshot;
+ERROR:  invalid input syntax for type pg_snapshot: "12:16:14,13"
+LINE 1: select '12:16:14,13'::pg_snapshot;
+               ^
+create temp table snapshot_test (
+	nr	integer,
+	snap	pg_snapshot
+);
+insert into snapshot_test values (1, '12:13:');
+insert into snapshot_test values (2, '12:20:13,15,18');
+insert into snapshot_test values (3, '100001:100009:100005,100007,100008');
+insert into snapshot_test values (4, '100:150:101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131');
+select snap from snapshot_test order by nr;
+                                                                snap                                                                 
+-------------------------------------------------------------------------------------------------------------------------------------
+ 12:13:
+ 12:20:13,15,18
+ 100001:100009:100005,100007,100008
+ 100:150:101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131
+(4 rows)
+
+select  pg_snapshot_xmin(snap),
+	pg_snapshot_xmax(snap),
+	pg_snapshot_xip(snap)
+from snapshot_test order by nr;
+ pg_snapshot_xmin | pg_snapshot_xmax | pg_snapshot_xip 
+------------------+------------------+-----------------
+               12 |               20 |              13
+               12 |               20 |              15
+               12 |               20 |              18
+           100001 |           100009 |          100005
+           100001 |           100009 |          100007
+           100001 |           100009 |          100008
+              100 |              150 |             101
+              100 |              150 |             102
+              100 |              150 |             103
+              100 |              150 |             104
+              100 |              150 |             105
+              100 |              150 |             106
+              100 |              150 |             107
+              100 |              150 |             108
+              100 |              150 |             109
+              100 |              150 |             110
+              100 |              150 |             111
+              100 |              150 |             112
+              100 |              150 |             113
+              100 |              150 |             114
+              100 |              150 |             115
+              100 |              150 |             116
+              100 |              150 |             117
+              100 |              150 |             118
+              100 |              150 |             119
+              100 |              150 |             120
+              100 |              150 |             121
+              100 |              150 |             122
+              100 |              150 |             123
+              100 |              150 |             124
+              100 |              150 |             125
+              100 |              150 |             126
+              100 |              150 |             127
+              100 |              150 |             128
+              100 |              150 |             129
+              100 |              150 |             130
+              100 |              150 |             131
+(37 rows)
+
+select id, pg_visible_in_snapshot(id::text::xid8, snap)
+from snapshot_test, generate_series(11, 21) id
+where nr = 2;
+ id | pg_visible_in_snapshot 
+----+------------------------
+ 11 | t
+ 12 | t
+ 13 | f
+ 14 | t
+ 15 | f
+ 16 | t
+ 17 | t
+ 18 | f
+ 19 | t
+ 20 | f
+ 21 | f
+(11 rows)
+
+-- test bsearch
+select id, pg_visible_in_snapshot(id::text::xid8, snap)
+from snapshot_test, generate_series(90, 160) id
+where nr = 4;
+ id  | pg_visible_in_snapshot 
+-----+------------------------
+  90 | t
+  91 | t
+  92 | t
+  93 | t
+  94 | t
+  95 | t
+  96 | t
+  97 | t
+  98 | t
+  99 | t
+ 100 | t
+ 101 | f
+ 102 | f
+ 103 | f
+ 104 | f
+ 105 | f
+ 106 | f
+ 107 | f
+ 108 | f
+ 109 | f
+ 110 | f
+ 111 | f
+ 112 | f
+ 113 | f
+ 114 | f
+ 115 | f
+ 116 | f
+ 117 | f
+ 118 | f
+ 119 | f
+ 120 | f
+ 121 | f
+ 122 | f
+ 123 | f
+ 124 | f
+ 125 | f
+ 126 | f
+ 127 | f
+ 128 | f
+ 129 | f
+ 130 | f
+ 131 | f
+ 132 | t
+ 133 | t
+ 134 | t
+ 135 | t
+ 136 | t
+ 137 | t
+ 138 | t
+ 139 | t
+ 140 | t
+ 141 | t
+ 142 | t
+ 143 | t
+ 144 | t
+ 145 | t
+ 146 | t
+ 147 | t
+ 148 | t
+ 149 | t
+ 150 | f
+ 151 | f
+ 152 | f
+ 153 | f
+ 154 | f
+ 155 | f
+ 156 | f
+ 157 | f
+ 158 | f
+ 159 | f
+ 160 | f
+(71 rows)
+
+-- test current values also
+select pg_current_xact_id() >= pg_snapshot_xmin(pg_current_snapshot());
+ ?column? 
+----------
+ t
+(1 row)
+
+-- we can't assume current is always less than xmax, however
+select pg_visible_in_snapshot(pg_current_xact_id(), pg_current_snapshot());
+ pg_visible_in_snapshot 
+------------------------
+ f
+(1 row)
+
+-- test 64bitness
+select pg_snapshot '1000100010001000:1000100010001100:1000100010001012,1000100010001013';
+                             pg_snapshot                             
+---------------------------------------------------------------------
+ 1000100010001000:1000100010001100:1000100010001012,1000100010001013
+(1 row)
+
+select pg_visible_in_snapshot('1000100010001012', '1000100010001000:1000100010001100:1000100010001012,1000100010001013');
+ pg_visible_in_snapshot 
+------------------------
+ f
+(1 row)
+
+select pg_visible_in_snapshot('1000100010001015', '1000100010001000:1000100010001100:1000100010001012,1000100010001013');
+ pg_visible_in_snapshot 
+------------------------
+ t
+(1 row)
+
+-- test 64bit overflow
+SELECT pg_snapshot '1:9223372036854775807:3';
+       pg_snapshot       
+-------------------------
+ 1:9223372036854775807:3
+(1 row)
+
+SELECT pg_snapshot '1:9223372036854775808:3';
+ERROR:  invalid input syntax for type pg_snapshot: "1:9223372036854775808:3"
+LINE 1: SELECT pg_snapshot '1:9223372036854775808:3';
+                           ^
+-- test pg_current_xact_id_if_assigned
+BEGIN;
+SELECT pg_current_xact_id_if_assigned() IS NULL;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT pg_current_xact_id() \gset
+SELECT pg_current_xact_id_if_assigned() IS NOT DISTINCT FROM xid8 :'pg_current_xact_id';
+ ?column? 
+----------
+ t
+(1 row)
+
+COMMIT;
+-- test xid status functions
+BEGIN;
+SELECT pg_current_xact_id() AS committed \gset
+COMMIT;
+BEGIN;
+SELECT pg_current_xact_id() AS rolledback \gset
+ROLLBACK;
+BEGIN;
+SELECT pg_current_xact_id() AS inprogress \gset
+SELECT pg_xact_status(:committed::text::xid8) AS committed;
+ committed 
+-----------
+ committed
+(1 row)
+
+SELECT pg_xact_status(:rolledback::text::xid8) AS rolledback;
+ rolledback 
+------------
+ aborted
+(1 row)
+
+SELECT pg_xact_status(:inprogress::text::xid8) AS inprogress;
+ inprogress  
+-------------
+ in progress
+(1 row)
+
+SELECT pg_xact_status('1'::xid8); -- BootstrapTransactionId is always committed
+ pg_xact_status 
+----------------
+ committed
+(1 row)
+
+SELECT pg_xact_status('2'::xid8); -- FrozenTransactionId is always committed
+ pg_xact_status 
+----------------
+ committed
+(1 row)
+
+SELECT pg_xact_status('3'::xid8); -- in regress testing FirstNormalTransactionId will always be behind oldestXmin
+ pg_xact_status 
+----------------
+ 
+(1 row)
+
+COMMIT;
+BEGIN;
+CREATE FUNCTION test_future_xid_status(xid8)
+RETURNS void
+LANGUAGE plpgsql
+AS
+$$
+BEGIN
+  PERFORM pg_xact_status($1);
+  RAISE EXCEPTION 'didn''t ERROR at xid in the future as expected';
+EXCEPTION
+  WHEN invalid_parameter_value THEN
+    RAISE NOTICE 'Got expected error for xid in the future';
+END;
+$$;
+SELECT test_future_xid_status((:inprogress + 10000)::text::xid8);
+NOTICE:  Got expected error for xid in the future
+ test_future_xid_status 
+------------------------
+ 
+(1 row)
+
+ROLLBACK;
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 8eca21823d..fb5c9139d1 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -1645,7 +1645,7 @@ from pg_locks l join pg_class c on l.relation = c.oid
 where virtualtransaction = (
         select virtualtransaction
         from pg_locks
-        where transactionid = txid_current()::integer)
+        where transactionid = pg_current_xact_id()::xid)
 and locktype = 'relation'
 and relnamespace != (select oid from pg_namespace where nspname = 'pg_catalog')
 and c.relname != 'my_locks'
@@ -1732,7 +1732,7 @@ from pg_locks l join pg_class c on l.relation = c.oid
 where virtualtransaction = (
         select virtualtransaction
         from pg_locks
-        where transactionid = txid_current()::integer)
+        where transactionid = pg_current_xact_id()::xid)
 and locktype = 'relation'
 and relnamespace != (select oid from pg_namespace where nspname = 'pg_catalog')
 and c.relname = 'my_locks'
diff --git a/src/test/regress/sql/hs_standby_functions.sql b/src/test/regress/sql/hs_standby_functions.sql
index 251bac0a43..b57f67ff8b 100644
--- a/src/test/regress/sql/hs_standby_functions.sql
+++ b/src/test/regress/sql/hs_standby_functions.sql
@@ -5,9 +5,9 @@
 --
 
 -- should fail
-select txid_current();
+select pg_current_xact_id();
 
-select length(txid_current_snapshot()::text) >= 4;
+select length(pg_current_snapshot()::text) >= 4;
 
 select pg_start_backup('should fail');
 select pg_switch_wal();
diff --git a/src/test/regress/sql/txid.sql b/src/test/regress/sql/txid.sql
index bd6decf0ef..8d5ac98a89 100644
--- a/src/test/regress/sql/txid.sql
+++ b/src/test/regress/sql/txid.sql
@@ -1,4 +1,7 @@
 -- txid_snapshot data type and related functions
+-- Note: these are backward-compatibility functions and types, and have been
+-- replaced by new xid8-based variants.  See xid.sql.  The txid variants will
+-- be removed in a future release.
 
 -- i/o
 select '12:13:'::txid_snapshot;
diff --git a/src/test/regress/sql/update.sql b/src/test/regress/sql/update.sql
index bb9c24e40f..8c558a7bc7 100644
--- a/src/test/regress/sql/update.sql
+++ b/src/test/regress/sql/update.sql
@@ -117,18 +117,16 @@ INSERT INTO upsert_test VALUES (1, 'Bat') ON CONFLICT(a)
 -- ON CONFLICT using system attributes in RETURNING, testing both the
 -- inserting and updating paths. See bug report at:
 -- https://www.postgresql.org/message-id/73436355-6432-49B1-92ED-1FE4F7E7E100%40finefun.com.au
-CREATE FUNCTION xid_current() RETURNS xid LANGUAGE SQL AS $$SELECT (txid_current() % ((1::int8<<32)))::text::xid;$$;
 INSERT INTO upsert_test VALUES (2, 'Beeble') ON CONFLICT(a)
   DO UPDATE SET (b, a) = (SELECT b || ', Excluded', a from upsert_test i WHERE i.a = excluded.a)
-  RETURNING tableoid::regclass, xmin = xid_current() AS xmin_correct, xmax = 0 AS xmax_correct;
+  RETURNING tableoid::regclass, xmin = pg_current_xact_id()::xid AS xmin_correct, xmax = 0 AS xmax_correct;
 -- currently xmax is set after a conflict - that's probably not good,
 -- but it seems worthwhile to have to be explicit if that changes.
 INSERT INTO upsert_test VALUES (2, 'Brox') ON CONFLICT(a)
   DO UPDATE SET (b, a) = (SELECT b || ', Excluded', a from upsert_test i WHERE i.a = excluded.a)
-  RETURNING tableoid::regclass, xmin = xid_current() AS xmin_correct, xmax = xid_current() AS xmax_correct;
+  RETURNING tableoid::regclass, xmin = pg_current_xact_id()::xid AS xmin_correct, xmax = pg_current_xact_id()::xid AS xmax_correct;
 
 
-DROP FUNCTION xid_current();
 DROP TABLE update_test;
 DROP TABLE upsert_test;
 
diff --git a/src/test/regress/sql/xid.sql b/src/test/regress/sql/xid.sql
index a4fbca5176..565714d462 100644
--- a/src/test/regress/sql/xid.sql
+++ b/src/test/regress/sql/xid.sql
@@ -46,3 +46,107 @@ create table xid8_t1 (x xid8);
 create index on xid8_t1 using btree(x);
 create index on xid8_t1 using hash(x);
 drop table xid8_t1;
+
+
+-- pg_snapshot data type and related functions
+
+-- Note: another set of tests similar to this exists in txid.sql, for a limited
+-- time (the relevant functions share C code)
+
+-- i/o
+select '12:13:'::pg_snapshot;
+select '12:18:14,16'::pg_snapshot;
+select '12:16:14,14'::pg_snapshot;
+
+-- errors
+select '31:12:'::pg_snapshot;
+select '0:1:'::pg_snapshot;
+select '12:13:0'::pg_snapshot;
+select '12:16:14,13'::pg_snapshot;
+
+create temp table snapshot_test (
+	nr	integer,
+	snap	pg_snapshot
+);
+
+insert into snapshot_test values (1, '12:13:');
+insert into snapshot_test values (2, '12:20:13,15,18');
+insert into snapshot_test values (3, '100001:100009:100005,100007,100008');
+insert into snapshot_test values (4, '100:150:101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131');
+select snap from snapshot_test order by nr;
+
+select  pg_snapshot_xmin(snap),
+	pg_snapshot_xmax(snap),
+	pg_snapshot_xip(snap)
+from snapshot_test order by nr;
+
+select id, pg_visible_in_snapshot(id::text::xid8, snap)
+from snapshot_test, generate_series(11, 21) id
+where nr = 2;
+
+-- test bsearch
+select id, pg_visible_in_snapshot(id::text::xid8, snap)
+from snapshot_test, generate_series(90, 160) id
+where nr = 4;
+
+-- test current values also
+select pg_current_xact_id() >= pg_snapshot_xmin(pg_current_snapshot());
+
+-- we can't assume current is always less than xmax, however
+
+select pg_visible_in_snapshot(pg_current_xact_id(), pg_current_snapshot());
+
+-- test 64bitness
+
+select pg_snapshot '1000100010001000:1000100010001100:1000100010001012,1000100010001013';
+select pg_visible_in_snapshot('1000100010001012', '1000100010001000:1000100010001100:1000100010001012,1000100010001013');
+select pg_visible_in_snapshot('1000100010001015', '1000100010001000:1000100010001100:1000100010001012,1000100010001013');
+
+-- test 64bit overflow
+SELECT pg_snapshot '1:9223372036854775807:3';
+SELECT pg_snapshot '1:9223372036854775808:3';
+
+-- test pg_current_xact_id_if_assigned
+BEGIN;
+SELECT pg_current_xact_id_if_assigned() IS NULL;
+SELECT pg_current_xact_id() \gset
+SELECT pg_current_xact_id_if_assigned() IS NOT DISTINCT FROM xid8 :'pg_current_xact_id';
+COMMIT;
+
+-- test xid status functions
+BEGIN;
+SELECT pg_current_xact_id() AS committed \gset
+COMMIT;
+
+BEGIN;
+SELECT pg_current_xact_id() AS rolledback \gset
+ROLLBACK;
+
+BEGIN;
+SELECT pg_current_xact_id() AS inprogress \gset
+
+SELECT pg_xact_status(:committed::text::xid8) AS committed;
+SELECT pg_xact_status(:rolledback::text::xid8) AS rolledback;
+SELECT pg_xact_status(:inprogress::text::xid8) AS inprogress;
+SELECT pg_xact_status('1'::xid8); -- BootstrapTransactionId is always committed
+SELECT pg_xact_status('2'::xid8); -- FrozenTransactionId is always committed
+SELECT pg_xact_status('3'::xid8); -- in regress testing FirstNormalTransactionId will always be behind oldestXmin
+
+COMMIT;
+
+BEGIN;
+CREATE FUNCTION test_future_xid_status(xid8)
+RETURNS void
+LANGUAGE plpgsql
+AS
+$$
+BEGIN
+  PERFORM pg_xact_status($1);
+  RAISE EXCEPTION 'didn''t ERROR at xid in the future as expected';
+EXCEPTION
+  WHEN invalid_parameter_value THEN
+    RAISE NOTICE 'Got expected error for xid in the future';
+END;
+$$;
+SELECT test_future_xid_status((:inprogress + 10000)::text::xid8);
+ROLLBACK;