pg_depend The catalog pg_depend records the dependency
relationships between database objects. This information allows
DROP commands to find which other objects must be dropped
by DROP CASCADE or prevent dropping in the DROP
RESTRICT case.
See also pg_shdepend,
which performs a similar function for dependencies involving objects
that are shared across a database cluster.
Table 51.18. pg_depend Columns
| Name | Type | References | Description |
|---|---|---|---|
classid | oid | | The OID of the system catalog the dependent object is in |
objid | oid | any OID column | The OID of the specific dependent object |
objsubid | int4 | For a table column, this is the column number (the
objid and classid refer to the
table itself). For all other object types, this column is
zero.
| |
refclassid | oid | | The OID of the system catalog the referenced object is in |
refobjid | oid | any OID column | The OID of the specific referenced object |
refobjsubid | int4 | For a table column, this is the column number (the
refobjid and refclassid refer
to the table itself). For all other object types, this column
is zero.
| |
deptype | char | A code defining the specific semantics of this dependency relationship; see text |
In all cases, a pg_depend entry indicates that the
referenced object cannot be dropped without also dropping the dependent
object. However, there are several subflavors identified by
deptype:
DEPENDENCY_NORMAL (n) A normal relationship between separately-created objects. The
dependent object can be dropped without affecting the
referenced object. The referenced object can only be dropped
by specifying CASCADE, in which case the dependent
object is dropped, too. Example: a table column has a normal
dependency on its data type.
DEPENDENCY_AUTO (a) The dependent object can be dropped separately from the
referenced object, and should be automatically dropped
(regardless of RESTRICT or CASCADE
mode) if the referenced object is dropped. Example: a named
constraint on a table is made autodependent on the table, so
that it will go away if the table is dropped.
DEPENDENCY_INTERNAL (i) The dependent object was created as part of creation of the
referenced object, and is really just a part of its internal
implementation. A DROP of the dependent object
will be disallowed outright (we'll tell the user to issue a
DROP against the referenced object, instead). A
DROP of the referenced object will be propagated
through to drop the dependent object whether
CASCADE is specified or not. Example: a trigger
that's created to enforce a foreign-key constraint is made
internally dependent on the constraint's
pg_constraint entry.
DEPENDENCY_EXTENSION (e) The dependent object is a member of the extension that is
the referenced object (see
pg_extension).
The dependent object can be dropped only via
DROP EXTENSION on the referenced object. Functionally
this dependency type acts the same as an internal dependency, but
it's kept separate for clarity and to simplify pg_dump.
DEPENDENCY_AUTO_EXTENSION (x)The dependent object is not a member of the extension that is the referenced object (and so should not be ignored by pg_dump), but cannot function without it and should be dropped when the extension itself is. The dependent object may be dropped on its own as well.
DEPENDENCY_PIN (p) There is no dependent object; this type of entry is a signal
that the system itself depends on the referenced object, and so
that object must never be deleted. Entries of this type are
created only by initdb. The columns for the
dependent object contain zeroes.
Other dependency flavors might be needed in future.