The pg_description table can store an optional description or comment for each database object. Descriptions can be manipulated with the COMMENT command. Client applications can view the descriptions by joining with this table. Many built-in system objects have comments associated with them that are shown by psql's \d commands.
Table 3-7. pg_description Columns
|objoid||oid||any oid attribute||The oid of the object this description pertains to|
|classoid||oid||pg_class.oid||The oid of the system catalog this object appears in|
|objsubid||int4||For a comment on a table attribute, this is the attribute's column number (the objoid and classoid refer to the table itself). For all other object types, this field is presently zero.|
|description||text||Arbitrary text that serves as the description of this object.|