catalogs.sgml

PostgreSQL7.4.6 for Linux

   relationships between database objects.  This information allows
   <command>DROP</> commands to find which other objects must be dropped
   by <command>DROP CASCADE</> or prevent dropping in the <command>DROP
   RESTRICT</> case.
  </para>

  <table>
   <title><structname>pg_depend</> Columns</title>

   <tgroup cols=4>
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Type</entry>
      <entry>References</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><structfield>classid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
      <entry>The OID of the system catalog the dependent object is in</entry>
     </row>

     <row>
      <entry><structfield>objid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry>any OID column</entry>
      <entry>The OID of the specific dependent object</entry>
     </row>

     <row>
      <entry><structfield>objsubid</structfield></entry>
      <entry><type>int4</type></entry>
      <entry></entry>
      <entry>
       For a table column, this is the column number (the
       <structfield>objid</> and <structfield>classid</> refer to the
       table itself).  For all other object types, this column is
       zero.
      </entry>
     </row>

     <row>
      <entry><structfield>refclassid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
      <entry>The OID of the system catalog the referenced object is in</entry>
     </row>

     <row>
      <entry><structfield>refobjid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry>any OID column</entry>
      <entry>The OID of the specific referenced object</entry>
     </row>

     <row>
      <entry><structfield>refobjsubid</structfield></entry>
      <entry><type>int4</type></entry>
      <entry></entry>
      <entry>
       For a table column, this is the column number (the
       <structfield>refobjid</> and <structfield>refclassid</> refer
       to the table itself).  For all other object types, this column
       is zero.
      </entry>
     </row>

     <row>
      <entry><structfield>deptype</structfield></entry>
      <entry><type>char</type></entry>
      <entry></entry>
      <entry>
       A code defining the specific semantics of this dependency relationship; see text.
      </entry>
     </row>

    </tbody>
   </tgroup>
  </table>

  <para>
   In all cases, a <structname>pg_depend</structname> entry indicates that the
   referenced object may not be dropped without also dropping the dependent
   object.  However, there are several subflavors identified by
   <structfield>deptype</>:

   <variablelist>
    <varlistentry>
     <term><symbol>DEPENDENCY_NORMAL</> (<literal>n</>)</term>
     <listitem>
      <para>
       A normal relationship between separately-created objects.  The
       dependent object may be dropped without affecting the
       referenced object.  The referenced object may only be dropped
       by specifying <literal>CASCADE</>, in which case the dependent
       object is dropped, too.  Example: a table column has a normal
       dependency on its data type.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>DEPENDENCY_AUTO</> (<literal>a</>)</term>
     <listitem>
      <para>
       The dependent object can be dropped separately from the
       referenced object, and should be automatically dropped
       (regardless of <literal>RESTRICT</> or <literal>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.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>DEPENDENCY_INTERNAL</> (<literal>i</>)</term>
     <listitem>
      <para>
       The dependent object was created as part of creation of the
       referenced object, and is really just a part of its internal
       implementation.  A <command>DROP</> of the dependent object
       will be disallowed outright (we'll tell the user to issue a
       <command>DROP</> against the referenced object, instead).  A
       <command>DROP</> of the referenced object will be propagated
       through to drop the dependent object whether
       <command>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
       <structname>pg_constraint</> entry.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>DEPENDENCY_PIN</> (<literal>p</>)</term>
     <listitem>
      <para>
       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 <command>initdb</command>.  The columns for the
       dependent object contain zeroes.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>

   Other dependency flavors may be needed in future.
  </para>

 </sect1>


 <sect1 id="catalog-pg-description">
  <title><structname>pg_description</structname></title>

  <indexterm zone="catalog-pg-description">
   <primary>pg_description</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_description</> can store an optional description or
   comment for each database object.  Descriptions can be manipulated
   with the <command>COMMENT</command> command and viewed with
   <application>psql</application>'s <literal>\d</literal> commands.
   Descriptions of many built-in system objects are provided in the initial
   contents of <structname>pg_description</structname>.
  </para>

  <table>
   <title><structname>pg_description</> Columns</title>

   <tgroup cols=4>
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Type</entry>
      <entry>References</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><structfield>objoid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry>any OID column</entry>
      <entry>The OID of the object this description pertains to</entry>
     </row>

     <row>
      <entry><structfield>classoid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
      <entry>The OID of the system catalog this object appears in</entry>
     </row>

     <row>
      <entry><structfield>objsubid</structfield></entry>
      <entry><type>int4</type></entry>
      <entry></entry>
      <entry>
       For a comment on a table column, this is the column number (the
       <structfield>objoid</> and <structfield>classoid</> refer to
       the table itself).  For all other object types, this column is
       zero.
      </entry>
     </row>

     <row>
      <entry><structfield>description</structfield></entry>
      <entry><type>text</type></entry>
      <entry></entry>
      <entry>Arbitrary text that serves as the description of this object.</entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-group">
  <title><structname>pg_group</structname></title>

  <indexterm zone="catalog-pg-group">
   <primary>pg_group</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_group</structname> defines groups and stores what users belong to what
   groups.  Groups are created with the <command>CREATE
   GROUP</command> command.  Consult <xref linkend="user-manag"> for information
   about user privilege management.
  </para>

  <para>
   Because user and group identities are cluster-wide,
   <structname>pg_group</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_group</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_group</> Columns</title>

   <tgroup cols=4>
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Type</entry>
      <entry>References</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><structfield>groname</structfield></entry>
      <entry><type>name</type></entry>
      <entry></entry>
      <entry>Name of the group</entry>
     </row>

     <row>
      <entry><structfield>grosysid</structfield></entry>
      <entry><type>int4</type></entry>
      <entry></entry>
      <entry>An arbitrary number to identify this group</entry>
     </row>

     <row>
      <entry><structfield>grolist</structfield></entry>
      <entry><type>int4[]</type></entry>
      <entry><literal><link linkend="catalog-pg-shadow"><structname>pg_shadow</structname></link>.usesysid</literal></entry>
      <entry>An array containing the IDs of the users in this group</entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-index">
  <title><structname>pg_index</structname></title>

  <indexterm zone="catalog-pg-index">
   <primary>pg_index</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_index</structname> contains part of the information
   about indexes.  The rest is mostly in
   <structname>pg_class</structname>.
  </para>

  <table>
   <title><structname>pg_index</> Columns</title>

   <tgroup cols=4>
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Type</entry>
      <entry>References</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><structfield>indexrelid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
      <entry>The OID of the <structname>pg_class</> entry for this index</entry>
     </row>

     <row>
      <entry><structfield>indrelid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
      <entry>The OID of the <structname>pg_class</> entry for the table this index is for</entry>
     </row>

     <row>
      <entry><structfield>indkey</structfield></entry>
      <entry><type>int2vector</type></entry>
      <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</literal></entry>
      <entry>
       This is an array of <structfield>indnatts</structfield> (up to
       <symbol>INDEX_MAX_KEYS</symbol>) values that indicate which
       table columns this index indexes.  For example a value of
       <literal>1 3</literal> would mean that the first and the third table
       columns make up the index key.  A zero in this array indicates that the
       corresponding index attribute is an expression over the table columns,
       rather than a simple column reference.
      </entry>
     </row>

     <row>
      <entry><structfield>indclass</structfield></entry>
      <entry><type>oidvector</type></entry>
      <entry><link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link>.oid</entry>
      <entry>
       For each column in the index key this contains the OID of
       the operator class to use.  See
       <structname>pg_opclass</structname> for details.
      </entry>
     </row>

     <row>
      <entry><structfield>indnatts</structfield></entry>
      <entry><type>int2</type></entry>
      <entry></entry>
      <entry>The number of columns in the index (duplicates
      <literal>pg_class.relnatts</literal>)</entry>
     </row>

     <row>
      <entry><structfield>indisunique</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>If true, this is a unique index.</entry>
     </row>

     <row>
      <entry><structfield>indisprimary</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>If true, this index represents the primary key of the table.
      (<structfield>indisunique</> should always be true when this is true.)</entry>
     </row>

     <row>
      <entry><structfield>indisclustered</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>If true, the table was last clustered on this index.</entry>
     </row>

     <row>
      <entry><structfield>indexprs</structfield></entry>
      <entry><type>text</type></entry>
      <entry></entry>
      <entry>Expression trees (in <function>nodeToString()</function> representation)
      for index attributes that are not simple column references.  This is a
      list with one element for each zero entry in <structfield>indkey</>.
      Null if all index attributes are simple references.</entry>
     </row>

     <row>
      <entry><structfield>indpred</structfield></entry>
      <entry><type>text</type></entry>
      <entr