Suppose I create a table in Postgresql with a comment on a column:

create table t1 (
   c1 varchar(10)
);
comment on column t1.c1 is 'foo';

Some time later, I decide to add another column:

alter table t1 add column c2 varchar(20);

I want to look up the comment contents of the first column, and associate with the new column:

select comment_text from (what?) where table_name = 't1' and column_name = 'c1'

The (what?) is going to be a system table, but after having looked around in pgAdmin and searching on the web I haven't learnt its name.

Ideally I'd like to be able to:

comment on column t1.c1 is (select ...);

but I have a feeling that's stretching things a bit far. Thanks for any ideas.

Update: based on the suggestions I received here, I wound up writing a program to automate the task of transferring comments, as part of a larger process of changing the datatype of a Postgresql column. You can read about that on my blog.