pg_attrdef
   The catalog pg_attrdef stores column default
   values.  The main information about columns is stored in
   pg_attribute.
   Only columns for which a default value has been explicitly set will have
   an entry here.
  
Table 51.6. pg_attrdef Columns
| Column Type Description | 
|---|
| 
        Row identifier | 
| 
        The table this column belongs to | 
| 
        The number of the column | 
| 
        
       The column default value, in  |