release.sgml

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

       <para>
        Add <function>md5(bytea)</> (Abhijit Menon-Sen)
       </para>
       <para>
        <function>md5(text)</> already existed.
       </para>
      </listitem>

      <listitem>
       <para>
        Add support for <command>numeric ^ numeric</> based on
        <function>power(numeric, numeric)</>
       </para>
       <para>
        The function already existed, but there was no operator assigned
        to it.
       </para>
      </listitem>

      <listitem>
       <para>
        Fix <type>NUMERIC</> modulus by properly truncating the quotient
        during computation (Bruce)
       </para>
       <para>
        In previous releases, modulus for large values sometimes
        returned negative results due to rounding of the quotient.
       </para>
      </listitem>

      <listitem>
       <para>
        Add a function <function>lastval()</> (Dennis Bj&ouml;rklund)
       </para>
       <para>
        <function>lastval()</> is a simplified version of
        <function>currval()</>. It automatically determines the proper
        sequence name based on the most recent <function>nextval()</> or
        <function>setval()</> call performed by the current session.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <function>to_timestamp(DOUBLE PRECISION) (Michael Glaesemann)</>
       </para>
       <para>
        Converts Unix seconds since 1970 to a <type>TIMESTAMP WITH
        TIMEZONE</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <function>pg_postmaster_start_time()</> function (Euler
        Taveira de Oliveira, Matthias Schmidt)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow the full use of time zone names in <command>AT TIME
        ZONE</>, not just the short list previously available (Magnus)
       </para>
       <para>
        Previously, only a predefined list of time zone names were
        supported by <command>AT TIME ZONE</>. Now any supported time
        zone name can be used, e.g.:
        <programlisting>
         SELECT CURRENT_TIMESTAMP AT TIME ZONE 'Europe/London';
        </programlisting>
        In the above query, the time zone used is adjusted based on the
        daylight saving time rules that were in effect on the supplied
        date.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <function>GREATEST()</> and <function>LEAST()</> variadic
        functions (Pavel Stehule)
       </para>
       <para>
        These functions take a variable number of arguments and return
        the greatest or least value among the arguments.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <function>pg_column_size()</> (Mark Kirkwood)
       </para>
       <para>
        This returns storage size of a column, which might be compressed.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <function>regexp_replace()</> (Atsushi Ogawa)
       </para>
       <para>
        This allows regular expression replacement, like sed. An optional
        flag argument allows selection of global (replace all) and
        case-insensitive modes.
       </para>
      </listitem>

      <listitem>
       <para>
        Fix interval division and multiplication (Bruce)
       </para>
       <para>
        Previous versions sometimes returned unjustified results, like
        <command>'4 months'::interval / 5</> returning <command>'1 mon
        -6 days'</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Fix roundoff behavior in timestamp, time, and interval output (Tom)
       </para>
       <para>
        This fixes some cases in which the seconds field would be shown as
        <literal>60</> instead of incrementing the higher-order fields.
       </para>
      </listitem>

      <listitem>
       <para>
        Add a separate day field to type <type>interval</> so a one day
        interval can be distinguished from a 24 hour interval (Michael
        Glaesemann)
       </para>
       <para>
        Days that contain a daylight saving time adjustment are not 24
        hours long, but typically 23 or 25 hours.  This change creates a
        conceptual distinction between intervals of <quote>so many days</>
        and intervals of <quote>so many hours</>.  Adding
        <literal>1 day</> to a timestamp now gives the same local time on
        the next day even if a daylight saving time adjustment occurs
        between, whereas adding <literal>24 hours</> will give a different
        local time when this happens.  For example, under US DST rules:
        <programlisting>
         '2005-04-03 00:00:00-05' + '1 day' = '2005-04-04 00:00:00-04'
         '2005-04-03 00:00:00-05' + '24 hours' = '2005-04-04 01:00:00-04'
        </programlisting>
       </para>
      </listitem>

      <listitem>
       <para>
        Add <function>justify_days()</> and <function>justify_hours()</>
        (Michael Glaesemann)
       </para>
       <para>
        These functions, respectively, adjust days to an appropriate
        number of full months and days, and adjust hours to an
        appropriate number of full days and hours.
       </para>
      </listitem>

      <listitem>
       <para>
        Move <filename>/contrib/dbsize</> into the backend, and rename
        some of the functions (Dave Page, Andreas Pflug)
       </para>
       <para>
        <itemizedlist>
  
         <listitem>
          <para>
            <function>pg_tablespace_size()</>
          </para>
         </listitem>

         <listitem>
          <para>
           <function>pg_database_size()</>
          </para>
         </listitem>

         <listitem>
          <para>
           <function>pg_relation_size()</>
          </para>
         </listitem>

         <listitem>
          <para>
           <function>pg_total_relation_size()</>
          </para>
         </listitem>

         <listitem>
          <para>
           <function>pg_size_pretty()</>
          </para>
         </listitem>
 
        </itemizedlist>
       </para>
       <para>
        <function>pg_total_relation_size()</> includes indexes and TOAST
        tables.
       </para>
      </listitem>

      <listitem>
       <para>
        Add functions for read-only file access to the cluster directory
        (Dave Page, Andreas Pflug)
       </para>
       <para>
        <itemizedlist>
  
         <listitem>
          <para>
           <function>pg_stat_file()</>
          </para>
         </listitem>

         <listitem>
          <para>
           <function>pg_read_file()</>
          </para>
         </listitem>

         <listitem>
          <para>
           <function>pg_ls_dir()</>
          </para>
         </listitem>

        </itemizedlist>
       </para>
      </listitem>
      
      <listitem>
       <para>
        Add <function>pg_reload_conf()</> to force reloading of the
        configuration files (Dave Page, Andreas Pflug)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <function>pg_rotate_logfile()</> to force rotation of the
        server log file (Dave Page, Andreas Pflug)
       </para>
      </listitem>

      <listitem>
       <para>
        Change <literal>pg_stat_*</> views to include TOAST tables (Tom)
       </para>
      </listitem>

     </itemizedlist>
    </sect3>
  
  
    <sect3>
     <title>Encoding and Locale Changes</title>
     <itemizedlist>
  
      <listitem>
       <para>
        Rename some encodings to be more consistent and to follow
        international standards (Bruce)
       </para>
       <para>
        <itemizedlist>
  
         <listitem>
          <para>
           <literal>UNICODE</> is now <literal>UTF8</>
          </para>
         </listitem>

         <listitem>
          <para>
           <literal>ALT</> is now <literal>WIN866</>
          </para>
         </listitem>

         <listitem>
          <para>
           <literal>WIN</> is now <literal>WIN1251</>
          </para>
         </listitem>

         <listitem>
          <para>
          <literal>TCVN</> is now <literal>WIN1258</>
          </para>
         </listitem>

        </itemizedlist>
       </para>

       <para>
        The original names still work.
       </para>
      </listitem>

      <listitem>
       <para>
        Add support for <literal>WIN1252</> encoding (Roland Volkmann)
       </para>
      </listitem>

      <listitem>
       <para>
        Add support for four-byte <literal>UTF8</> characters (John
        Hansen)
       </para>
       <para>
        Previously only one, two, and three-byte <literal>UTF8</> characters
        were supported. This is particularly important for support for
        some Chinese character sets.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow direct conversion between <literal>EUC_JP</> and
        <literal>SJIS</> to improve performance (Atsushi Ogawa)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow the UTF8 encoding to work on Windows (Magnus)
       </para>
       <para>
        This is done by mapping UTF8 to the Windows-native UTF16 
        implementation.
       </para>
      </listitem>

     </itemizedlist>
    </sect3>
  
  
    <sect3>
     <title>General Server-Side Language Changes</title>
     <itemizedlist>
  
      <listitem>
       <para>
        Fix <command>ALTER LANGUAGE RENAME</> (Sergey Yatskevich)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow function characteristics, like strictness and volatility,
        to be modified via <command>ALTER FUNCTION</> (Neil)
       </para>
      </listitem>

      <listitem>
       <para>
        Increase the maximum number of function arguments to 100 (Tom)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow SQL and PL/PgSQL functions to use <command>OUT</> and
        <command>INOUT</> parameters (Tom)
       </para>
       <para>
        <command>OUT</> is an alternate way for a function to return
        values. Instead of using <command>RETURN</>, values can be
        returned by assigning to parameters declared as <command>OUT</> or
        <command>INOUT</>.  This is notationally simpler in some cases,
        particularly so when multiple values need to be returned.
        While returning multiple values from a function
        was possible in previous releases, this greatly simplifies the
        process.  (The feature will be extended to other server-side
        languages in future releases.)
       </para>
      </listitem>

      <listitem>
       <para>
        Move language handler functions into the <literal>pg_catal