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 52.6. pg_attrdef Columns
| Name | Type | References | Description |
|---|---|---|---|
oid | oid | Row identifier (hidden attribute; must be explicitly selected) | |
adrelid | oid | | The table this column belongs to |
adnum | int2 | | The number of the column |
adbin | pg_node_tree | The internal representation of the column default value | |
adsrc | text | 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.