records the dependency relationships between database objects and
shared objects, such as roles. This information allows
PostgreSQL to ensure that those
objects are unreferenced before attempting to delete them.
pg_depend, which performs a similar
function for dependencies involving objects within a single
Unlike most system catalogs,
pg_shdepend is shared across all databases of
a cluster: there is only one copy of
pg_shdepend per cluster, not one per
||The OID of the database the dependent object is in, or zero for a shared object|
||The OID of the system catalog the dependent object is in|
||any OID column||The OID of the specific dependent object|
||For a table column, this is the column number (the
||The OID of the system catalog the referenced object is in (must be a shared catalog)|
||any OID column||The OID of the specific referenced object|
||A code defining the specific semantics of this dependency relationship; see text|
In all cases, a
entry indicates that the referenced object cannot be dropped
without also dropping the dependent object. However, there are
several subflavors identified by
The referenced object (which must be a role) is the owner of the dependent object.
The referenced object (which must be a role) is
mentioned in the ACL (access control list, i.e., privileges
list) of the dependent object. (A
SHARED_DEPENDENCY_ACL entry is not made for
the owner of the object, since the owner will have a
The referenced object (which must be a role) is mentioned as the target of a dependent policy object.
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. Note in particular that the current definition only supports roles as referenced objects.
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