You can "compress" it by one step with USING, like:

alter table abc alter COLUMN abc_integer set data type abc_enum_type using case when abc_integer == 1 THEN 'hi'::abc_enum_type ELSE 'hello'::abc_enum_type END; 

and then renaming the column abc_integer to abc_enum.

If that what you want it works on 9.3

Btw! Mind default values.

You can "compress" it by one step with USING, like:

alter table abc alter COLUMN abc_integer set data type abc_enum_type using case when abc_integer == 1 THEN 'hi'::abc_enum_type ELSE 'hello'::abc_enum_type END; 

and then renaming the column abc_integer to abc_enum.

If that what you want it works on 9.3

Btw! Mind default values.

Edit The way you do it does not lock the table. While altering column type will!