catalogs.sgml

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

      <entry></entry>
      <entry>
       Always -1 in storage, but when loaded into a row descriptor
       in memory this may be updated to cache the offset of the attribute
       within the row.
      </entry>
     </row>

     <row>
      <entry><structfield>atttypmod</structfield></entry>
      <entry><type>int4</type></entry>
      <entry></entry>
      <entry>
       <structfield>atttypmod</structfield> records type-specific data
       supplied at table creation time (for example, the maximum
       length of a <type>varchar</type> column).  It is passed to
       type-specific input functions and length coercion functions.
       The value will generally be -1 for types that do not need <structfield>atttypmod</>.
      </entry>
     </row>

     <row>
      <entry><structfield>attbyval</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       A copy of <literal>pg_type.typbyval</> of this column's type
      </entry>
     </row>

     <row>
      <entry><structfield>attstorage</structfield></entry>
      <entry><type>char</type></entry>
      <entry></entry>
      <entry>
       Normally a copy of <literal>pg_type.typstorage</> of this
       column's type.  For TOAST-able data types, this can be altered
       after column creation to control storage policy.
      </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>

  <para>
   In a dropped column's <structname>pg_attribute</structname> entry,
   <structfield>atttypid</structfield> is reset to zero, but 
   <structfield>attlen</structfield> and the other fields copied from
   <structname>pg_type</> are still valid.  This arrangement is needed
   to cope with the situation where the dropped column's data type was
   later dropped, and so there is no <structname>pg_type</> row anymore.
   <structfield>attlen</structfield> and the other fields can be used
   to interpret the contents of a row of the table.
  </para>
 </sect1>


 <sect1 id="catalog-pg-authid">
  <title><structname>pg_authid</structname></title>

  <indexterm zone="catalog-pg-authid">
   <primary>pg_authid</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_authid</structname> contains information about
   database authorization identifiers (roles).  A role subsumes the concepts
   of <quote>users</> and <quote>groups</>.  A user is essentially just a
   role with the <structfield>rolcanlogin</> flag set.  Any role (with or
   without <structfield>rolcanlogin</>) may have other roles as members; see
   <link linkend="catalog-pg-auth-members"><structname>pg_auth_members</structname></link>.
  </para>

  <para>
   Since this catalog contains passwords, it must not be publicly readable.
   <link linkend="view-pg-roles"><structname>pg_roles</structname></link>
   is a publicly readable view on
   <structname>pg_authid</structname> that blanks out the password field.
  </para>

  <para>
   <xref linkend="user-manag"> contains detailed information about user and
   privilege management.
  </para>

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

  <table>
   <title><structname>pg_authid</> 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>rolname</structfield></entry>
      <entry><type>name</type></entry>
      <entry></entry>
      <entry>Role name</entry>
     </row>

     <row>
      <entry><structfield>rolsuper</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>Role has superuser privileges</entry>
     </row>

     <row>
      <entry><structfield>rolinherit</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>Role automatically inherits privileges of roles it is a
       member of</entry>
     </row>

     <row>
      <entry><structfield>rolcreaterole</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>Role may create more roles</entry>
     </row>

     <row>
      <entry><structfield>rolcreatedb</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>Role may create databases</entry>
     </row>

     <row>
      <entry><structfield>rolcatupdate</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       Role may update system catalogs directly.  (Even a superuser may not do
       this unless this column is true.)
      </entry>
     </row>

     <row>
      <entry><structfield>rolcanlogin</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>
       Role may log in, that is, this role can be given as the initial
       session authorization identifier.
      </entry>
     </row>

     <row>
      <entry><structfield>rolconnlimit</structfield></entry>
      <entry><type>int4</type></entry>
      <entry></entry>
      <entry>
       For roles that can log in, this sets maximum number of concurrent 
       connections this role can make.  -1 means no limit.
      </entry>
     </row>

     <row>
      <entry><structfield>rolpassword</structfield></entry>
      <entry><type>text</type></entry>
      <entry></entry>
      <entry>Password (possibly encrypted); NULL if none</entry>
     </row>

     <row>
      <entry><structfield>rolvaliduntil</structfield></entry>
      <entry><type>timestamptz</type></entry>
      <entry></entry>
      <entry>Password expiry time (only used for password authentication);
       NULL if no expiration</entry>
     </row>

     <row>
      <entry><structfield>rolconfig</structfield></entry>
      <entry><type>text[]</type></entry>
      <entry></entry>
      <entry>Session defaults for run-time configuration variables</entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-auth-members">
  <title><structname>pg_auth_members</structname></title>

  <indexterm zone="catalog-pg-auth-members">
   <primary>pg_auth_members</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_auth_members</structname> shows the membership
   relations between roles.  Any non-circular set of relationships is allowed.
  </para>

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

  <table>
   <title><structname>pg_auth_members</> 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>roleid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
      <entry>ID of a role that has a member</entry>
     </row>

     <row>
      <entry><structfield>member</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
      <entry>ID of a role that is a member of <structfield>roleid</></entry>
     </row>

     <row>
      <entry><structfield>grantor</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
      <entry>ID of the role that granted this membership</entry>
     </row>

     <row>
      <entry><structfield>admin_option</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>True if <structfield>member</> may grant membership in
       <structfield>roleid</> to others</entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-autovacuum">
  <title><structname>pg_autovacuum</structname></title>

  <indexterm zone="catalog-pg-autovacuum">
   <primary>pg_autovacuum</primary>
  </indexterm>

  <indexterm zone="catalog-pg-autovacuum">
   <primary>autovacuum</primary>
   <secondary>table-specific configuration</secondary>
  </indexterm>

  <para>
   The catalog <structname>pg_autovacuum</structname> stores optional
   per-relation configuration parameters for <xref linkend="autovacuum" endterm="autovacuum-title">.
   If there is an entry here for a particular relation, the given
   parameters will be used for autovacuuming that table.  If no entry
   is present, the system-wide defaults will be used.
  </para>

  <table>
   <title><structname>pg_autovacuum</> 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>vacrelid</structfield></entry>
      <entry><type>oid</type></entry>
      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
      <entry>The table this entry is for</entry>
     </row>

     <row>
      <entry><structfield>enabled</structfield></entry>
      <entry><type>bool</type></entry>
      <entry></entry>
      <entry>If false, this table is never autovacuumed</entry>
     </row>

     <row>
      <entry><structfield>vac_base_thresh</structfield></entry>
      <entry><type>integer</type></entry>
      <entry></entry>
      <entry>Minimum number of modified tuples before vacuum</entry>
     </row>

     <row>
      <entry><structfield>vac_scale_factor</structfield></entry>
      <entry><type>float4</type></entry>
      <entry></entry>
      <entry>Multiplier for reltuples to add to
       <structfield>vac_base_thresh</></entry>
     </row>

     <row>
      <entry><structfield>anl_base_thresh</structfield></entry>
      <entry><type>integer</type></entry>
      <entry></entry>
      <entry>Minimum number of modified tuples before analyze</entry>