51.6. 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 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.