pg_dependThe 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.
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