doc/src/sgml/ref/pg_walsummary.sgml

   1 <!--
   2 doc/src/sgml/ref/pg_walsummary.sgml
   3 PostgreSQL documentation
   4 -->
   5
   6 <refentry id="app-pgwalsummary">
   7  <indexterm zone="app-pgwalsummary">
   8   <primary>pg_walsummary</primary>
   9  </indexterm>
  10
  11  <refmeta>
  12   <refentrytitle><application>pg_walsummary</application></refentrytitle>
  13   <manvolnum>1</manvolnum>
  14   <refmiscinfo>Application</refmiscinfo>
  15  </refmeta>
  16
  17  <refnamediv>
  18   <refname>pg_walsummary</refname>
  19   <refpurpose>print contents of WAL summary files</refpurpose>
  20  </refnamediv>
  21
  22  <refsynopsisdiv>
  23   <cmdsynopsis>
  24    <command>pg_walsummary</command>
  25    <arg rep="repeat" choice="opt"><replaceable>option</replaceable></arg>
  26    <arg rep="repeat"><replaceable>file</replaceable></arg>
  27   </cmdsynopsis>
  28  </refsynopsisdiv>
  29
  30  <refsect1>
  31   <title>Description</title>
  32   <para>
  33    <application>pg_walsummary</application> is used to print the contents of
  34    WAL summary files. These binary files are found with the
  35    <literal>pg_wal/summaries</literal> subdirectory of the data directory,
  36    and can be converted to text using this tool. This is not ordinarily
  37    necessary, since WAL summary files primarily exist to support
  38    <link linkend="backup-incremental-backup">incremental backup</link>,
  39    but it may be useful for debugging purposes.
  40   </para>
  41
  42   <para>
  43    A WAL summary file is indexed by tablespace OID, relation OID, and relation
  44    fork. For each relation fork, it stores the list of blocks that were
  45    modified by WAL within the range summarized in the file. It can also
  46    store a "limit block," which is 0 if the relation fork was created or
  47    truncated within the relevant WAL range, and otherwise the shortest length
  48    to which the relation fork was truncated. If the relation fork was not
  49    created, deleted, or truncated within the relevant WAL range, the limit
  50    block is undefined or infinite and will not be printed by this tool.
  51   </para>
  52  </refsect1>
  53
  54  <refsect1>
  55   <title>Options</title>
  56
  57    <para>
  58     <variablelist>
  59      <varlistentry>
  60       <term><option>-i</option></term>
  61       <term><option>--individual</option></term>
  62       <listitem>
  63        <para>
  64         By default, <literal>pg_walsummary</literal> prints one line of output
  65         for each range of one or more consecutive modified blocks. This can
  66         make the output a lot briefer, since a relation where all blocks from
  67         0 through 999 were modified will produce only one line of output rather
  68         than 1000 separate lines. This option requests a separate line of
  69         output for every modified block.
  70        </para>
  71       </listitem>
  72      </varlistentry>
  73
  74      <varlistentry>
  75       <term><option>-q</option></term>
  76       <term><option>--quiet</option></term>
  77       <listitem>
  78        <para>
  79         Do not print any output, except for errors. This can be useful
  80         when you want to know whether a WAL summary file can be successfully
  81         parsed but don't care about the contents.
  82        </para>
  83       </listitem>
  84      </varlistentry>
  85
  86      <varlistentry>
  87       <term><option>-V</option></term>
  88       <term><option>--version</option></term>
  89       <listitem>
  90        <para>
  91         Display version information, then exit.
  92        </para>
  93       </listitem>
  94      </varlistentry>
  95
  96      <varlistentry>
  97        <term><option>-?</option></term>
  98        <term><option>--help</option></term>
  99        <listitem>
 100        <para>
 101        Shows help about <application>pg_walsummary</application> command line
 102        arguments, and exits.
 103        </para>
 104        </listitem>
 105      </varlistentry>
 106
 107     </variablelist>
 108    </para>
 109
 110  </refsect1>
 111
 112  <refsect1>
 113   <title>Environment</title>
 114
 115   <para>
 116    The environment variable <envar>PG_COLOR</envar> specifies whether to use
 117    color in diagnostic messages. Possible values are
 118    <literal>always</literal>, <literal>auto</literal> and
 119    <literal>never</literal>.
 120   </para>
 121  </refsect1>
 122
 123  <refsect1>
 124   <title>See Also</title>
 125
 126   <simplelist type="inline">
 127    <member><xref linkend="app-pgbasebackup"/></member>
 128    <member><xref linkend="app-pgcombinebackup"/></member>
 129   </simplelist>
 130  </refsect1>
 131
 132 </refentry>