55.6. 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 55.6. pg_attrdef Columns
Column Type Description  | 
|---|
 Row identifier  | 
 The table this column belongs to  | 
 The number of the column  | 
  The column default value, in   |