Postgres MVCC
Version information
These are system columns, and can be viewed just like any other columns.
E.g., a few rows from table R of assignment 7:
jao=# select *, xmin, xmax, ctid from r where r_id between 1000076 and 1000088 order by r_id;
r_id | r_2 | r_10 | r_1p | r_10p | r_50p | r_filler | s_id | xmin | xmax | ctid
---------+-----+------+------+-------+-------+------------+------+---------+------+------------
1000076 | 76 | 76 | 76 | 6 | 0 | xxxxxxxxxx | 76 | 1927367 | 0 | (8333,117)
1000077 | 77 | 77 | 77 | 7 | 1 | xxxxxxxxxx | 77 | 1927367 | 0 | (8333,118)
1000078 | 78 | 78 | 78 | 8 | 0 | xxxxxxxxxx | 78 | 1927367 | 0 | (8333,119)
1000079 | 79 | 79 | 79 | 9 | 1 | xxxxxxxxxx | 79 | 1927367 | 0 | (8333,120)
1000080 | 80 | 80 | 80 | 0 | 0 | xxxxxxxxxx | 80 | 1927367 | 0 | (8334,1)
1000081 | 81 | 81 | 81 | 1 | 1 | xxxxxxxxxx | 81 | 1927367 | 0 | (8334,2)
1000082 | 82 | 82 | 82 | 2 | 0 | xxxxxxxxxx | 82 | 1927367 | 0 | (8334,3)
1000083 | 83 | 83 | 83 | 3 | 1 | xxxxxxxxxx | 83 | 1927367 | 0 | (8334,4)
1000084 | 84 | 84 | 84 | 4 | 0 | xxxxxxxxxx | 84 | 1927367 | 0 | (8334,5)
1000085 | 85 | 85 | 85 | 5 | 1 | xxxxxxxxxx | 85 | 1927367 | 0 | (8334,6)
1000086 | 86 | 86 | 86 | 6 | 0 | xxxxxxxxxx | 86 | 1927367 | 0 | (8334,7)
1000087 | 87 | 87 | 87 | 7 | 1 | xxxxxxxxxx | 87 | 1927367 | 0 | (8334,8)
1000088 | 88 | 88 | 88 | 8 | 0 | xxxxxxxxxx | 88 | 1927367 | 0 | (8334,9)
(13 rows)
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