52.6. pg_attrdef
| Up | Chapter 52. System Catalogs | Home |

## 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.

| Up |
| Home |