be a partitioned table,
     allowing hierarchies to be created.
    </para>
   </glossdef>
   <glossdef>
    <para>
     In reference to a <glossterm linkend="glossary-window-function">window function</glossterm>
     in a <glossterm linkend="glossary-query">query</glossterm>,
     a partition is a user-defined criterion that identifies which neighboring
     <glossterm linkend="glossary-tuple">rows</glossterm>
     of the <glossterm linkend="glossary-result-set">query's result set</glossterm>
     can be considered by the function.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-partitioned-table">
   <glossterm>Partitioned table (relation)</glossterm>
   <glossdef>
    <para>
     A <glossterm linkend="glossary-relation">relation</glossterm> that is
     in semantic terms the same as a <glossterm linkend="glossary-table">table</glossterm>,
     but whose storage is distributed across several
     <glossterm linkend="glossary-partition">partitions</glossterm>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-postmaster">
   <glossterm>Postmaster (process)</glossterm>
   <glossdef>
    <para>
      The very first process of an <glossterm linkend="glossary-instance">instance</glossterm>.
      It starts and manages the
      <glossterm linkend="glossary-auxiliary-proc">auxiliary processes</glossterm>
      and creates <glossterm linkend="glossary-backend">backend processes</glossterm>
      on demand.
    </para>
    <para>
     For more information, see
     <xref linkend="server-start"/>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-primary-key">
   <glossterm>Primary key</glossterm>
   <glossdef>
    <para>
     A special case of a
     <glossterm linkend="glossary-unique-constraint">unique constraint</glossterm>
     defined on a
     <glossterm linkend="glossary-table">table</glossterm> or other
     <glossterm linkend="glossary-relation">relation</glossterm> that also
     guarantees that all of the
     <glossterm linkend="glossary-attribute">attributes</glossterm>
     within the <glossterm linkend="glossary-primary-key">primary key</glossterm>
     do not have <glossterm linkend="glossary-null">null</glossterm> values.
     As the name implies, there can be only one
     primary key per table, though it is possible to have multiple unique
     constraints that also have no null-capable attributes.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-primary-server">
   <glossterm>Primary (server)</glossterm>
   <glossdef>
    <para>
     When two or more <glossterm linkend="glossary-database">databases</glossterm>
     are linked via <glossterm linkend="glossary-replication">replication</glossterm>,
     the <glossterm linkend="glossary-server">server</glossterm>
     that is considered the authoritative source of information is called
     the <firstterm>primary</firstterm>,
     also known as a <firstterm>master</firstterm>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-procedure">
   <glossterm>Procedure (routine)</glossterm>
   <glossdef>
    <para>
     A type of routine.
     Their distinctive qualities are that they do not return values,
     and that they are allowed to make transactional statements such
     as <command>COMMIT</command> and <command>ROLLBACK</command>.
     They are invoked via the <command>CALL</command> command.
    </para>
    <para>
     For more information, see
     <xref linkend="sql-createprocedure"/>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-query">
   <glossterm>Query</glossterm>
   <glossdef>
    <para>
     A request sent by a client to a <glossterm linkend="glossary-backend">backend</glossterm>,
     usually to return results or to modify data on the database.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-planner">
   <glossterm>Query planner</glossterm>
   <glossdef>
    <para>
     The part of <productname>PostgreSQL</productname>