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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>53.18. pg_depend</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="catalog-pg-default-acl.html" title="53.17. pg_default_acl" /><link rel="next" href="catalog-pg-description.html" title="53.19. pg_description" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">53.18. <code class="structname">pg_depend</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalog-pg-default-acl.html" title="53.17. pg_default_acl">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="catalogs.html" title="Chapter 53. System Catalogs">Up</a></td><th width="60%" align="center">Chapter 53. System Catalogs</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="catalog-pg-description.html" title="53.19. pg_description">Next</a></td></tr></table><hr /></div><div class="sect1" id="CATALOG-PG-DEPEND"><div class="titlepage"><div><div><h2 class="title" style="clear: both">53.18. <code class="structname">pg_depend</code> <a href="#CATALOG-PG-DEPEND" class="id_link">#</a></h2></div></div></div><a id="id-1.10.4.20.2" class="indexterm"></a><p>
The catalog <code class="structname">pg_depend</code> records the dependency
relationships between database objects. This information allows
<code class="command">DROP</code> commands to find which other objects must be dropped
by <code class="command">DROP CASCADE</code> or prevent dropping in the <code class="command">DROP
RESTRICT</code> case.
</p><p>
See also <a class="link" href="catalog-pg-shdepend.html" title="53.48. pg_shdepend"><code class="structname">pg_shdepend</code></a>,
which performs a similar function for dependencies involving objects
that are shared across a database cluster.
</p><div class="table" id="id-1.10.4.20.5"><p class="title"><strong>Table 53.18. <code class="structname">pg_depend</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_depend Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
Column Type
</p>
<p>
Description
</p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">classid</code> <code class="type">oid</code>
(references <a class="link" href="catalog-pg-class.html" title="53.11. pg_class"><code class="structname">pg_class</code></a>.<code class="structfield">oid</code>)
</p>
<p>
The OID of the system catalog the dependent object is in
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">objid</code> <code class="type">oid</code>
(references any OID column)
</p>
<p>
The OID of the specific dependent object
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">objsubid</code> <code class="type">int4</code>
</p>
<p>
For a table column, this is the column number (the
<code class="structfield">objid</code> and <code class="structfield">classid</code> refer to the
table itself). For all other object types, this column is
zero.
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">refclassid</code> <code class="type">oid</code>
(references <a class="link" href="catalog-pg-class.html" title="53.11. pg_class"><code class="structname">pg_class</code></a>.<code class="structfield">oid</code>)
</p>
<p>
The OID of the system catalog the referenced object is in
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">refobjid</code> <code class="type">oid</code>
(references any OID column)
</p>
<p>
The OID of the specific referenced object
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">refobjsubid</code> <code class="type">int4</code>
</p>
<p>
For a table column, this is the column number (the
<code class="structfield">refobjid</code> and <code class="structfield">refclassid</code> refer
to the table itself). For all other object types, this column
is zero.
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">deptype</code> <code class="type">char</code>
</p>
<p>
A code defining the specific semantics of this dependency relationship; see text
</p></td></tr></tbody></table></div></div><br class="table-break" /><p>
In all cases, a <code class="structname">pg_depend</code> entry indicates that the
referenced object cannot be dropped without also dropping the dependent
object. However, there are several subflavors identified by
<code class="structfield">deptype</code>:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="symbol">DEPENDENCY_NORMAL</code> (<code class="literal">n</code>)</span></dt><dd><p>
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 <code class="literal">CASCADE</code>, in which case the dependent
object is dropped, too. Example: a table column has a normal
dependency on its data type.
</p></dd><dt><span class="term"><code class="symbol">DEPENDENCY_AUTO</code> (<code class="literal">a</code>)</span></dt><dd><p>
The dependent object can be dropped separately from the
referenced object, and should be automatically dropped
(regardless of <code class="literal">RESTRICT</code> or <code class="literal">CASCADE</code>
mode) if the referenced object is dropped. Example: a named
constraint on a table is made auto-dependent on the table, so
that it will go away if the table is dropped.
</p></dd><dt><span class="term"><code class="symbol">DEPENDENCY_INTERNAL</code> (<code class="literal">i</code>)</span></dt><dd><p>
The dependent object was created as part of creation of the
referenced object, and is really just a part of its internal
implementation. A direct <code class="command">DROP</code> of the dependent
object will be disallowed outright (we'll tell the user to issue
a <code class="command">DROP</code> against the referenced object, instead).
A <code class="command">DROP</code> of the referenced object will result in
automatically dropping the dependent object
whether <code class="literal">CASCADE</code> is specified or not. If the
dependent object has to be dropped due to a dependency on some other
object being removed, its drop is converted to a drop of the referenced
object, so that <code class="literal">NORMAL</code> and <code class="literal">AUTO</code>
dependencies of the dependent object behave much like they were
dependencies of the referenced object.
Example: a view's <code class="literal">ON SELECT</code> rule is made
internally dependent on the view, preventing it from being dropped
while the view remains. Dependencies of the rule (such as tables it
refers to) act as if they were dependencies of the view.
</p></dd><dt><span class="term"><code class="symbol">DEPENDENCY_PARTITION_PRI</code> (<code class="literal">P</code>)<br /></span><span class="term"><code class="symbol">DEPENDENCY_PARTITION_SEC</code> (<code class="literal">S</code>)</span></dt><dd><p>
The dependent object was created as part of creation of the
referenced object, and is really just a part of its internal
implementation; however, unlike <code class="literal">INTERNAL</code>,
there is more than one such referenced object. The dependent object
must not be dropped unless at least one of these referenced objects
is dropped; if any one is, the dependent object should be dropped
whether or not <code class="literal">CASCADE</code> is specified. Also
unlike <code class="literal">INTERNAL</code>, a drop of some other object
that the dependent object depends on does not result in automatic
deletion of any partition-referenced object. Hence, if the drop
does not cascade to at least one of these objects via some other
path, it will be refused. (In most cases, the dependent object
shares all its non-partition dependencies with at least one
partition-referenced object, so that this restriction does not
result in blocking any cascaded delete.)
Primary and secondary partition dependencies behave identically
except that the primary dependency is preferred for use in error
messages; hence, a partition-dependent object should have one
primary partition dependency and one or more secondary partition
dependencies.
Note that partition dependencies are made in addition to, not
instead of, any dependencies the object would normally have. This
simplifies <code class="command">ATTACH/DETACH PARTITION</code> operations:
the partition dependencies need only be added or removed.
Example: a child partitioned index is made partition-dependent
on both the partition table it is on and the parent partitioned
index, so that it goes away if either of those is dropped, but
not otherwise. The dependency on the parent index is primary,
so that if the user tries to drop the child partitioned index,
the error message will suggest dropping the parent index instead
(not the table).
</p></dd><dt><span class="term"><code class="symbol">DEPENDENCY_EXTENSION</code> (<code class="literal">e</code>)</span></dt><dd><p>
The dependent object is a member of the <em class="firstterm">extension</em> that is
the referenced object (see
<a class="link" href="catalog-pg-extension.html" title="53.22. pg_extension"><code class="structname">pg_extension</code></a>).
The dependent object can be dropped only via
<a class="link" href="sql-dropextension.html" title="DROP EXTENSION"><code class="command">DROP EXTENSION</code></a> on the referenced object.
Functionally this dependency type acts the same as
an <code class="literal">INTERNAL</code> dependency, but it's kept separate for
clarity and to simplify <span class="application">pg_dump</span>.
</p></dd><dt><span class="term"><code class="symbol">DEPENDENCY_AUTO_EXTENSION</code> (<code class="literal">x</code>)</span></dt><dd><p>
The dependent object is not a member of the extension that is the
referenced object (and so it should not be ignored
by <span class="application">pg_dump</span>), but it cannot function
without the extension and should be auto-dropped if the extension is.
The dependent object may be dropped on its own as well.
Functionally this dependency type acts the same as
an <code class="literal">AUTO</code> dependency, but it's kept separate for
clarity and to simplify <span class="application">pg_dump</span>.
</p></dd></dl></div><p>
Other dependency flavors might be needed in future.
</p><p>
Note that it's quite possible for two objects to be linked by more than
one <code class="structname">pg_depend</code> entry. For example, a child
partitioned index would have both a partition-type dependency on its
associated partition table, and an auto dependency on each column of
that table that it indexes. This sort of situation expresses the union
of multiple dependency semantics. A dependent object can be dropped
without <code class="literal">CASCADE</code> if any of its dependencies satisfies
its condition for automatic dropping. Conversely, all the
dependencies' restrictions about which objects must be dropped together
must be satisfied.
</p><p>
Most objects created during <span class="application">initdb</span> are
considered <span class="quote">“<span class="quote">pinned</span>”</span>, which means that the system itself
depends on them. Therefore, they are never allowed to be dropped.
Also, knowing that pinned objects will not be dropped, the dependency
mechanism doesn't bother to make <code class="structname">pg_depend</code>
entries showing dependencies on them. Thus, for example, a table
column of type <code class="type">numeric</code> notionally has
a <code class="literal">NORMAL</code> dependency on the <code class="type">numeric</code>
data type, but no such entry actually appears
in <code class="structname">pg_depend</code>.
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