I want a postgres function to generate ctid where condition for table migration based ctid

[yanliang lei]

for instance,
select * from  tabxxx where  ctid >= '(0,0)' AND ctid <= '(27,0)'
select * from  tabxxx where  ctid > '(27,0)' AND ctid <= '(57,0)'
select * from  tabxxx where  ctid > '(57,0)' AND ctid <= '(69,0)'

and so on


I want to generate a table ‘s  ctid condition automatically