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 51.6. 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.