Comments on PostgreSQL COMMENT

One of my favorite PostgreSQL features is the ability to attach a comment to an object.

COMMENT ON object_type object_name IS 'text'

For example, create a schema and add a comment to it:

create schema comment_demo;
comment on schema comment_demo is 'comments demo';

Append + to the psql meta-command to list schemas (\dn) to show comments:

stan=> \dn+ comment_demo
                  List of schemas
   Name       │ Owner │ Access privileges │  Description
──────────────┼───────┼───────────────────┼───────────────
 comment_demo │ stan  │                   │ comments demo

Set a comment to NULL to remove it:

comment on schema comment_demo is NULL;

Unless you have superuser privileges, you can’t add a comment to an object you don’t own:

stan=> comment on schema public is 'not owned by me';
ERROR:  must be owner of schema public

A comment can be attached to a wide variety of objects, as shown by psql’s auto-completion options:

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For more information, see the PostgreSQL documentation for COMMENT.