45.6. pg_attrdef

The catalog pg_attrdef stores column default values. The main information about columns is stored in pg_attribute (see below). Only columns that explicitly specify a default value (when the table is created or the column is added) will have an entry here.

Table 45-6. pg_attrdef Columns

adrelidoidpg_class.oidThe table this column belongs to
adnumint2pg_attribute.attnumThe number of the column
adbintext The internal representation of the column default value
adsrctext A human-readable representation of the default value

The adsrc field is historical, and is best not used, because it does not track outside changes that might affect the representation of the default value. Reverse-compiling the adbin field (with pg_get_expr for example) is a better way to display the default value.