Postgresql的隐藏系统列(3)

来源：未知责任编辑：责任编辑发表时间:2014-04-20 03:42　点击:次

------+------+------+------+--------+----+--------------

0 | 0 | 1852 | 0 | (0,2) | 2 | kenyonkenyon

0 | 0 | 1852 | 0 | (0,3) | 3 | kenyonkenyon

0 | 0 | 1853 | 0 | (0,4) | 4 | a

0 | 0 | 1854 | 0 | (0,8) | 7 | keke

1 | 1 | 1854 | 0 | (0,9) | 6 | kekeke

2 | 2 | 1854 | 0 | (0,10) | 5 | kenyon_test

0 | 0 | 1856 | 0 | (0,11) | 8 | jackson

这时我们可以看到其实delete的事务ID(xmin)值是1855，insert的(xmin)值是1856，ctid往上累计

最后看一下tableoid和pg_class中oid的关系,(oid不说了,系统中一般设置为false)

postgres=# select tableoid,cmin,cmax,xmin,xmax,ctid,* from test;

----------+------+------+------+------+--------+----+--------------

24601 | 0 | 0 | 1852 | 0 | (0,2) | 2 | kenyonkenyon

24601 | 0 | 0 | 1852 | 0 | (0,3) | 3 | kenyonkenyon

24601 | 0 | 0 | 1853 | 0 | (0,4) | 4 | a

24601 | 0 | 0 | 1854 | 0 | (0,8) | 7 | keke

24601 | 1 | 1 | 1854 | 0 | (0,9) | 6 | kekeke

24601 | 2 | 2 | 1854 | 0 | (0,10) | 5 | kenyon_test

24601 | 0 | 0 | 1856 | 0 | (0,11) | 8 | jackson

(7 rows) www.2cto.com

postgres=# select oid,relname,relfilenode,relkind from pg_class where oid = 24601;

oid | relname | relfilenode | relkind

-------+---------+-------------+---------

24601 | test | 24601 | r

作者 kenyon