doc/src/sgml/wal-for-extensions.sgml

   1 <!-- doc/src/sgml/wal-for-extensions.sgml -->
   2
   3 <chapter id="wal-for-extensions">
   4  <title>Write Ahead Logging for Extensions</title>
   5
   6   <para>
   7    Certain extensions, principally extensions that implement custom access
   8    methods, may need to perform write-ahead logging in order to ensure
   9    crash-safety. <productname>PostgreSQL</productname> provides two ways
  10    for extensions to achieve this goal.
  11   </para>
  12
  13   <para>
  14    First, extensions can choose to use <link linkend="generic-wal">generic
  15    WAL</link>, a special type of WAL record which describes changes to pages
  16    in a generic way. This method is simple to implement and does not require
  17    that an extension library be loaded in order to apply the records. However,
  18    generic WAL records will be ignored when performing logical decoding.
  19   </para>
  20
  21   <para>
  22    Second, extensions can choose to use a <link linkend="custom-rmgr">custom
  23    resource manager</link>. This method is more flexible, supports logical
  24    decoding, and can sometimes generate much smaller write-ahead log records
  25    than would be possible with generic WAL. However, it is more complex for an
  26    extension to implement.
  27   </para>
  28
  29 &generic-wal;
  30 &custom-rmgr;
  31
  32 </chapter>