52.6. pg_attrdef #

   The catalog pg_attrdef stores column default expressions and generation
   expressions. The main information about columns is stored in
   pg_attribute. Only columns for which a default expression or generation
   expression has been explicitly set will have an entry here.

   Table 52.6. pg_attrdef Columns

   Column Type

   Description

   oid oid

   Row identifier

   adrelid oid (references pg_class.oid)

   The table this column belongs to

   adnum int2 (references pg_attribute.attnum)

   The number of the column

   adbin pg_node_tree

   The column default or generation expression, in nodeToString()
   representation. Use pg_get_expr(adbin, adrelid) to convert it to an SQL
   expression.