Sophie: postgresql8.4-docs-8.4.12-0.1mdv2010.2 i586

postgresql8.4-docs-8.4.12-0.1mdv2010.2.i586.rpm

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><H1
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><A
NAME="MIGRATION"
>24.5. Migration Between Releases</A
></H1
><A
NAME="AEN31236"
></A
><A
NAME="AEN31238"
></A
><P
>   This section discusses how to migrate your database data from one
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> release to a newer one.
   The software installation procedure <I
CLASS="FOREIGNPHRASE"
>per se</I
> is not the
   subject of this section; those details are in <A
HREF="installation.html"
>Chapter 15</A
>.
  </P
><P
>   As a general rule, the internal data storage format is subject to
   change between major releases of <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> (where
   the number after the first dot changes). This does not apply to
   different minor releases under the same major release (where the
   number after the second dot changes); these always have compatible
   storage formats. For example, releases 8.1.1, 8.2.3, and 8.3 are
   not compatible, whereas 8.2.3 and 8.2.4 are. When you update
   between compatible versions, you can simply replace the executables
   and reuse the data directory on disk. Otherwise you need to back
   up your data and restore it on the new server.  This has to be done
   using <SPAN
CLASS="APPLICATION"
>pg_dump</SPAN
>; file system level backup methods
   obviously won't work. There are checks in place that prevent you
   from using a data directory with an incompatible version of
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>, so no great harm can be done by
   trying to start the wrong server version on a data directory.
  </P
><P
>   It is recommended that you use the <SPAN
CLASS="APPLICATION"
>pg_dump</SPAN
> and
   <SPAN
CLASS="APPLICATION"
>pg_dumpall</SPAN
> programs from the newer version of
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>, to take advantage of any enhancements
   that might have been made in these programs.  Current releases of the
   dump programs can read data from any server version back to 7.0.
  </P
><P
>   The least downtime can be achieved by installing the new server in
   a different directory and running both the old and the new servers
   in parallel, on different ports. Then you can use something like:

</P><PRE
CLASS="PROGRAMLISTING"
>pg_dumpall -p 5432 | psql -d postgres -p 6543</PRE
><P>

   to transfer your data.  Or use an intermediate file if you want.
   Then you can shut down the old server and start the new server at
   the port the old one was running at. You should make sure that the
   old database is not updated after you begin to run
   <SPAN
CLASS="APPLICATION"
>pg_dumpall</SPAN
>, otherwise you will lose that data. See <A
HREF="client-authentication.html"
>Chapter 19</A
> for information on how to prohibit
   access.
  </P
><P
>   It is also possible to use replication methods, such as
   <SPAN
CLASS="PRODUCTNAME"
>Slony</SPAN
>, to create a slave server with the updated version of
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>.  The slave can be on the same computer or
   a different computer.  Once it has synced up with the master server
   (running the older version of <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>), you can
   switch masters and make the slave the master and shut down the older
   database instance.  Such a switch-over results in only several seconds
   of downtime for an upgrade.
  </P
><P
>   If you cannot or do not want to run two servers in parallel, you can
   do the backup step before installing the new version, bring down
   the server, move the old version out of the way, install the new
   version, start the new server, and restore the data. For example:

</P><PRE
CLASS="PROGRAMLISTING"
>pg_dumpall &gt; backup
pg_ctl stop
mv /usr/local/pgsql /usr/local/pgsql.old
cd ~/postgresql-8.4.12
gmake install
initdb -D /usr/local/pgsql/data
postgres -D /usr/local/pgsql/data
psql -f backup postgres</PRE
><P>

   See <A
HREF="runtime.html"
>Chapter 17</A
> about ways to start and stop the
   server and other details. The installation instructions will advise
   you of strategic places to perform these steps.
  </P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>    When you <SPAN
CLASS="QUOTE"
>"move the old installation out of the way"</SPAN
>
    it might no longer be perfectly usable. Some of the executable programs
    contain absolute paths to various installed programs and data files.
    This is usually not a big problem, but if you plan on using two
    installations in parallel for a while you should assign them
    different installation directories at build time.  (This problem
    is rectified in <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> 8.0 and later, so long
    as you move all subdirectories containing installed files together;
    for example if <TT
CLASS="FILENAME"
>/usr/local/postgres/bin/</TT
> goes to
    <TT
CLASS="FILENAME"
>/usr/local/postgres.old/bin/</TT
>, then
    <TT
CLASS="FILENAME"
>/usr/local/postgres/share/</TT
> must go to
    <TT
CLASS="FILENAME"
>/usr/local/postgres.old/share/</TT
>.  In pre-8.0 releases
    moving an installation like this will not work.)
   </P
></BLOCKQUOTE
></DIV
><P
>   In practice you probably want to test your client applications on the
   new version before switching over completely.  This is another reason
   for setting up concurrent installations of old and new versions.  When
   testing a <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> major upgrade, consider the
   following categories of possible changes:
  </P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Administration</DT
><DD
><P
>      The capabilities available for administrators to monitor and control
      the server often change and improve in each major release.
     </P
></DD
><DT
>SQL</DT
><DD
><P
>      Typically this includes new SQL command capabilities and not changes
      in behavior, unless specifically mentioned in the release notes.
     </P
></DD
><DT
>Library API</DT
><DD
><P
>      Typically libraries like <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> only add new
      functionality, again unless mentioned in the release notes.
     </P
></DD
><DT
>System Catalogs</DT
><DD
><P
>      System catalog changes usually only affect database management tools.
     </P
></DD
><DT
>Server C-language API</DT
><DD
><P
>      This involved changes in the backend function API, which is written
      in the C programming language.  Such changes effect code that
      references backend functions deep inside the server.
     </P
></DD
></DL
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