catalogs.sgml

PostgreSQL7.4.6 for Linux

       the set.  So the <structfield>atttypid</structfield> (see
       above) refers to the type returned by this query, but the
       actual length of this attribute is the length (size) of an
       <type>oid</type>.  --- At least this is the theory.  All this
       is probably quite broken these days.
      </entry>
     </row>

     <row>
      <entry><structfield>attalign</structfield></entry>
      <entry><type>char</type></entry>
      <entry></entry>
      <entry>
       A copy of <literal>pg_type.typalign</> of this column's type
      </entry>
     </row>

     <row>
      <entry><structfield>attnotnull</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       This represents a not-null constraint.  It is possible to
       change this column to enable or disable the constraint.
      </entry>
     </row>

     <row>
      <entry><structfield>atthasdef</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       This column has a default value, in which case there will be a
       corresponding entry in the <structname>pg_attrdef</structname>
       catalog that actually defines the value.
      </entry>
     </row>

     <row>
      <entry><structfield>attisdropped</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       This column has been dropped and is no longer valid.  A dropped
       column is still physically present in the table, but is
       ignored by the parser and so cannot be accessed via SQL.
      </entry>
     </row>

     <row>
      <entry><structfield>attislocal</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       This column is defined locally in the relation.  Note that a column may
       be locally defined and inherited simultaneously.
      </entry>
     </row>

     <row>
      <entry><structfield>attinhcount</structfield></entry>
      <entry><type>int4</type></entry>
      <entry></entry>
      <entry>
       The number of direct ancestors this column has.  A column with a 
       nonzero number of ancestors cannot be dropped nor renamed.
      </entry>
     </row>

    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-cast">
  <title><structname>pg_cast</structname></title>

  <indexterm zone="catalog-pg-cast">
   <primary>pg_cast</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_cast</structname> stores data type conversion paths,
   both built-in paths and those defined with <command>CREATE CAST</command>.
  </para>

  <table>
   <title><structfield>pg_cast</> 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>castsource</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
      <entry>OID of the source data type</entry>
     </row>

     <row>
      <entry><structfield>casttarget</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
      <entry>OID of the target data type</entry>
     </row>

     <row>
      <entry><structfield>castfunc</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
      <entry>
       The OID of the function to use to perform this cast.  Zero is
       stored if the data types are binary compatible (that is, no
       run-time operation is needed to perform the cast).
      </entry>
     </row>

     <row>
      <entry><structfield>castcontext</structfield></entry>
      <entry><type>char</type></entry>
      <entry></entry>
      <entry>
       Indicates what contexts the cast may be invoked in.
       <literal>e</> means only as an explicit cast (using
       <literal>CAST</>, <literal>::</>, or function-call syntax).
       <literal>a</> means implicitly in assignment
       to a target column, as well as explicitly.
       <literal>i</> means implicitly in expressions, as well as the
       other cases.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-class">
  <title><structname>pg_class</structname></title>

  <indexterm zone="catalog-pg-class">
   <primary>pg_class</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_class</structname> catalogs tables and most
   everything else that has columns or is otherwise similar to a
   table.  This includes indexes (but see also
   <structname>pg_index</structname>), sequences, views, and some
   kinds of special relation; see <structfield>relkind</>.
   Below, when we mean all of these
   kinds of objects we speak of <quote>relations</quote>.  Not all
   columns are meaningful for all relation types.
  </para>

  <table>
   <title><structname>pg_class</> 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>relname</structfield></entry>
      <entry><type>name</type></entry>
      <entry></entry>
      <entry>Name of the table, index, view, etc.</entry>
     </row>

     <row>
      <entry><structfield>relnamespace</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
      <entry>
       The OID of the namespace that contains this relation
      </entry>
     </row>

     <row>
      <entry><structfield>reltype</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
      <entry>
       The OID of the data type that corresponds to this table, if any
       (zero for indexes, which have no <structname>pg_type</> entry)
      </entry>
     </row>

     <row>
      <entry><structfield>relowner</structfield></entry>
      <entry><type>int4</type></entry>
      <entry><literal><link linkend="catalog-pg-shadow"><structname>pg_shadow</structname></link>.usesysid</literal></entry>
      <entry>Owner of the relation</entry>
     </row>

     <row>
      <entry><structfield>relam</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-am"><structname>pg_am</structname></link>.oid</literal></entry>
      <entry>If this is an index, the access method used (B-tree, hash, etc.)</entry>
     </row>

     <row>
      <entry><structfield>relfilenode</structfield></entry>
      <entry><type>oid</type></entry>
      <entry></entry>
      <entry>Name of the on-disk file of this relation; 0 if none</entry>
     </row>

     <row>
      <entry><structfield>relpages</structfield></entry>
      <entry><type>int4</type></entry>
      <entry></entry>
      <entry>
       Size of the on-disk representation of this table in pages (size
       <symbol>BLCKSZ</symbol>).
       This is only an estimate used by the planner.
       It is updated by <command>VACUUM</command>,
       <command>ANALYZE</command>, and <command>CREATE INDEX</command>.
      </entry>
     </row>

     <row>
      <entry><structfield>reltuples</structfield></entry>
      <entry><type>float4</type></entry>
      <entry></entry>
      <entry>
       Number of rows in the table.
       This is only an estimate used by the planner.
       It is updated by <command>VACUUM</command>,
       <command>ANALYZE</command>, and <command>CREATE INDEX</command>.
      </entry>
     </row>

     <row>
      <entry><structfield>reltoastrelid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
      <entry>
       OID of the TOAST table associated with this table, 0 if none.
       The TOAST table stores large attributes <quote>out of
       line</quote> in a secondary table.
      </entry>
     </row>

     <row>
      <entry><structfield>reltoastidxid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
      <entry>
       For a TOAST table, the OID of its index.  0 if not a TOAST table.
      </entry>
     </row>

     <row>
      <entry><structfield>relhasindex</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       True if this is a table and it has (or recently had) any
       indexes. This is set by <command>CREATE INDEX</command>, but
       not cleared immediately by <command>DROP INDEX</command>.
       <command>VACUUM</command> clears <structfield>relhasindex</> if it finds the
       table has no indexes.
      </entry>
     </row>

     <row>
      <entry><structfield>relisshared</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>True if this table is shared across all databases in the
      cluster.  Only certain system catalogs (such as
      <structname>pg_database</structname>) are shared.</entry>
     </row>

     <row>
      <entry><structfield>relkind</structfield></entry>
      <entry><type>char</type></entry>
      <entry></entry>
      <entry>
       <literal>r</> = ordinary table, <literal>i</> = index,
       <literal>S</> = sequence, <literal>v</> = view, <literal>c</> =
       composite type, <literal>s</> = special, <literal>t</> = TOAST
       table
      </entry>
     </row>

     <row>
      <entry><structfield>relnatts</structfield></entry>
      <entry><type>int2</type></entry>
      <entry></entry>
      <entry>
       Number of user columns in the relation (system columns not
       counted).  There must be this many corresponding entries in
       <structname>pg_attribute</structname>.  See also
       <literal>pg_attribute.attnum</literal>.
      </entry>
     </row>

     <row>
      <entry><structfield>relchecks</structfield></entry>
      <entry><type>int2</type></entry>
      <entry></entry>
      <entry>
       Number of check constraints on the table; see
       <structname>pg_constraint</structname> catalog
      </entry>
     </row>

     <row>
      <entry><structfield>reltriggers</structfield></entry>
      <entry><type>int2</type></entry>
      <entry></entry>
      <entry>
       Number of triggers on the table; see
       <structname>pg_trigger</structname> catalog
      </entry>
     </row>

     <row>
      <entry><structfield>relukeys</structfield></entry>
      <entry><type>int2</type></entry>
      <entry></entry>
      <entry>unused  (<emphasis>not</emphasis> the number of unique keys)</entry>
     </row>

     <row>
      <entry><structfield>relfkeys</structfield></entry>
      <entry><type>int2</type></entry>
      <entry></entry>
      <entry>unused  (<emphasis>not</emphasis> the number of foreign keys on the table)</entry>
     </row>

     <row>
      <entry><structfield>relrefs</structfield></entry>
      <entry><type>int2</type></entry>
      <entry></entry>
      <entry>unused</entry>
     </row>

     <row>
      <entry><structfield>relhasoids</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       True if we generate an OID for each row of the relation.
      </entry>
     </row>

     <row>
      <entry><structfield>relhaspkey</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       True if the table has (or once had) a primary key.
      </entry>
     </row>

     <row>
      <entry><structfield>relhasrules</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>Table has rules; see
       <structname>pg_rewrite</structname> catalog
      </entry>
     </row>

     <row>
      <entry><structfield>relhassubclass</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>At least one table inherits from this one</entry>
     </row>

     <row>
      <entry><structfield>relacl</structfield></entry>
      <entry><type>aclitem[]</type></entry>
      <entry></entry>
      <entry>
       Access privileges; see the descriptions of
       <command>GRANT</command> and <command>REVOKE</command> for
       details.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </table>