pg 9.4为表函数引入了自动生成行号的功能，如下：
=# SELECT * FROM generate_series(4,1,-1) WITH ORDINALITY;
generate_series | ordinality
-----------------+------------
4 | 1
3 | 2
2 | 3
1 | 4
但是它不能用于普通表。在lightdb中，可以使用rownum对应，同时应用于表函数和表。如下：
zjh@postgres=# select rownum,rowid,id,v from big_table limit 10 offset 10;
rownum | rowid | id | v
--------+--------+-----+------------------------------
11 | (0,11) | 354 | fwisifwieisvfwismvmfeiwis354
12 | (0,12) | 398 | fwisifwieisvfwismvmfeiwis398
13 | (0,13) | 443 | fwisifwieisvfwismvmfeiwis443
14 | (0,14) | 588 | fwisifwieisvfwismvmfeiwis588
15 | (0,15) | 611 | fwisifwieisvfwismvmfeiwis611
16 | (0,16) | 686 | fwisifwieisvfwismvmfeiwis686
17 | (0,17) | 742 | fwisifwieisvfwismvmfeiwis742
18 | (0,18) | 762 | fwisifwieisvfwismvmfeiwis762
19 | (0,19) | 791 | fwisifwieisvfwismvmfeiwis791
20 | (0,20) | 850 | fwisifwieisvfwismvmfeiwis850
(10 rows)
zjh@postgres=# SELECT rownum,x FROM generate_series(4,1,-1) x;
rownum | x
--------+---
1 | 4
2 | 3
3 | 2
4 | 1
(4 rows)
具有更好的通用性。
https://paquier.xyz/postgresql-2/postgres-9-4-feature-highlight-with-ordinality/
http://www.light-pg.com/docs/lightdb/13.8-22.3/functions-srf.html
标签：ordinaly,lightdb,series,9.4,postgresql,rownum,generate,postgres From： https://www.cnblogs.com/lightdb/p/16980582.html