text: -- txid_snapshot data type and related functions
  
  -- i/o
  select '12:13:'::txid_snapshot;
  select '12:18:14,16'::txid_snapshot;
  select '12:16:14,14'::txid_snapshot;
  
  -- errors
  select '31:12:'::txid_snapshot;
  select '0:1:'::txid_snapshot;
  select '12:13:0'::txid_snapshot;
  select '12:16:14,13'::txid_snapshot;
  
  create temp table snapshot_test (
  	nr	integer,
  	snap	txid_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  txid_snapshot_xmin(snap),
  	txid_snapshot_xmax(snap),
  	txid_snapshot_xip(snap)
  from snapshot_test order by nr;
  
  select id, txid_visible_in_snapshot(id, snap)
  from snapshot_test, generate_series(11, 21) id
  where nr = 2;
  
  -- test bsearch
  select id, txid_visible_in_snapshot(id, snap)
  from snapshot_test, generate_series(90, 160) id
  where nr = 4;
  
  -- test current values also
  select txid_current() >= txid_snapshot_xmin(txid_current_snapshot());
  
  -- we can't assume current is always less than xmax, however
  
  select txid_visible_in_snapshot(txid_current(), txid_current_snapshot());
  
  -- test 64bitness
  
  select txid_snapshot '1000100010001000:1000100010001100:1000100010001012,1000100010001013';
  select txid_visible_in_snapshot('1000100010001012', '1000100010001000:1000100010001100:1000100010001012,1000100010001013');
  select txid_visible_in_snapshot('1000100010001015', '1000100010001000:1000100010001100:1000100010001012,1000100010001013');
  
  -- test 64bit overflow
  SELECT txid_snapshot '1:9223372036854775807:3';
  SELECT txid_snapshot '1:9223372036854775808:3';
  
  -- test txid_current_if_assigned
  BEGIN;
  SELECT txid_current_if_assigned() IS NULL;
  SELECT txid_current() \gset
  SELECT txid_current_if_assigned() IS NOT DISTINCT FROM BIGINT :'txid_current';
  COMMIT;
  