Postgres \copy from CSV: how to format range variables?
Removing the explicit cast to tstrange worked. The new CSV file looks like

t_range|field1
'[2014-06-02 07:00:00,infinity)'|'sometext1'
'[2014-06-02 07:00:00,infinity)'|'sometext2'


It seems to me that \copy is fine with automatically attempting to cast to the appropriate datatypes, but the explicit cast causes it to choke.

One can also simplify the CSV file a bit in this case by removing the quotes:

t_range|field1
[2014-06-02 07:00:00,infinity)|sometext1
[2014-06-02 07:00:00,infinity)|sometext2


and modifying the import command:

\copy my_table FROM 'my.csv' DELIMITER '|' CSV HEADER;