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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>pg_amcheck</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="app-ecpg.html" title="ecpg" /><link rel="next" href="app-pgbasebackup.html" title="pg_basebackup" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center"><span xmlns="http://www.w3.org/1999/xhtml" class="application">pg_amcheck</span></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="app-ecpg.html" title="ecpg">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="reference-client.html" title="PostgreSQL Client Applications">Up</a></td><th width="60%" align="center">PostgreSQL Client Applications</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="app-pgbasebackup.html" title="pg_basebackup">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="APP-PGAMCHECK"><div class="titlepage"></div><a id="id-1.9.4.9.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle"><span class="application">pg_amcheck</span></span></h2><p>pg_amcheck — checks for corruption in one or more
<span class="productname">PostgreSQL</span> databases</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p id="id-1.9.4.9.4.1"><code class="command">pg_amcheck</code> [<em class="replaceable"><code>option</code></em>...] [<em class="replaceable"><code>dbname</code></em>]</p></div></div><div class="refsect1" id="id-1.9.4.9.5"><h2>Description</h2><p>
<span class="application">pg_amcheck</span> supports running
<a class="xref" href="amcheck.html" title="F.2. amcheck">amcheck</a>'s corruption checking functions against one or
more databases, with options to select which schemas, tables and indexes to
check, which kinds of checking to perform, and whether to perform the checks
in parallel, and if so, the number of parallel connections to establish and
use.
</p><p>
Only table relations and btree indexes are currently supported. Other
relation types are silently skipped.
</p><p>
If <code class="literal">dbname</code> is specified, it should be the name of a
single database to check, and no other database selection options should
be present. Otherwise, if any database selection options are present,
all matching databases will be checked. If no such options are present,
the default database will be checked. Database selection options include
<code class="option">--all</code>, <code class="option">--database</code> and
<code class="option">--exclude-database</code>. They also include
<code class="option">--relation</code>, <code class="option">--exclude-relation</code>,
<code class="option">--table</code>, <code class="option">--exclude-table</code>,
<code class="option">--index</code>, and <code class="option">--exclude-index</code>,
but only when such options are used with a three-part pattern
(e.g. <code class="option">mydb*.myschema*.myrel*</code>). Finally, they include
<code class="option">--schema</code> and <code class="option">--exclude-schema</code>
when such options are used with a two-part pattern
(e.g. <code class="option">mydb*.myschema*</code>).
</p><p>
<em class="replaceable"><code>dbname</code></em> can also be a
<a class="link" href="libpq-connect.html#LIBPQ-CONNSTRING" title="34.1.1. Connection Strings">connection string</a>.
</p></div><div class="refsect1" id="id-1.9.4.9.6"><h2>Options</h2><p>
The following command-line options control what is checked:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-a</code><br /></span><span class="term"><code class="option">--all</code></span></dt><dd><p>
Check all databases, except for any excluded via
<code class="option">--exclude-database</code>.
</p></dd><dt><span class="term"><code class="option">-d <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--database=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Check databases matching the specified
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>,
except for any excluded by <code class="option">--exclude-database</code>.
This option can be specified more than once.
</p></dd><dt><span class="term"><code class="option">-D <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--exclude-database=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Exclude databases matching the given
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>.
This option can be specified more than once.
</p></dd><dt><span class="term"><code class="option">-i <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--index=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Check indexes matching the specified
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>,
unless they are otherwise excluded.
This option can be specified more than once.
</p><p>
This is similar to the <code class="option">--relation</code> option, except that
it applies only to indexes, not tables.
</p></dd><dt><span class="term"><code class="option">-I <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--exclude-index=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Exclude indexes matching the specified
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>.
This option can be specified more than once.
</p><p>
This is similar to the <code class="option">--exclude-relation</code> option,
except that it applies only to indexes, not tables.
</p></dd><dt><span class="term"><code class="option">-r <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--relation=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Check relations matching the specified
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>,
unless they are otherwise excluded.
This option can be specified more than once.
</p><p>
Patterns may be unqualified, e.g. <code class="literal">myrel*</code>, or they
may be schema-qualified, e.g. <code class="literal">myschema*.myrel*</code> or
database-qualified and schema-qualified, e.g.
<code class="literal">mydb*.myscheam*.myrel*</code>. A database-qualified
pattern will add matching databases to the list of databases to be
checked.
</p></dd><dt><span class="term"><code class="option">-R <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--exclude-relation=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Exclude relations matching the specified
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>.
This option can be specified more than once.
</p><p>
As with <code class="option">--relation</code>, the
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a> may be unqualified, schema-qualified,
or database- and schema-qualified.
</p></dd><dt><span class="term"><code class="option">-s <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--schema=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Check tables and indexes in schemas matching the specified
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>, unless they are otherwise excluded.
This option can be specified more than once.
</p><p>
To select only tables in schemas matching a particular pattern,
consider using something like
<code class="literal">--table=SCHEMAPAT.* --no-dependent-indexes</code>.
To select only indexes, consider using something like
<code class="literal">--index=SCHEMAPAT.*</code>.
</p><p>
A schema pattern may be database-qualified. For example, you may
write <code class="literal">--schema=mydb*.myschema*</code> to select
schemas matching <code class="literal">myschema*</code> in databases matching
<code class="literal">mydb*</code>.
</p></dd><dt><span class="term"><code class="option">-S <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--exclude-schema=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Exclude tables and indexes in schemas matching the specified
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>.
This option can be specified more than once.
</p><p>
As with <code class="option">--schema</code>, the pattern may be
database-qualified.
</p></dd><dt><span class="term"><code class="option">-t <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--table=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Check tables matching the specified
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>,
unless they are otherwise excluded.
This option can be specified more than once.
</p><p>
This is similar to the <code class="option">--relation</code> option, except that
it applies only to tables, not indexes.
</p></dd><dt><span class="term"><code class="option">-T <em class="replaceable"><code>pattern</code></em></code><br /></span><span class="term"><code class="option">--exclude-table=<em class="replaceable"><code>pattern</code></em></code></span></dt><dd><p>
Exclude tables matching the specified
<a class="link" href="app-psql.html#APP-PSQL-PATTERNS" title="Patterns"><em class="replaceable"><code>pattern</code></em></a>.
This option can be specified more than once.
</p><p>
This is similar to the <code class="option">--exclude-relation</code> option,
except that it applies only to tables, not indexes.
</p></dd><dt><span class="term"><code class="option">--no-dependent-indexes</code></span></dt><dd><p>
By default, if a table is checked, any btree indexes of that table
will also be checked, even if they are not explicitly selected by
an option such as <code class="literal">--index</code> or
<code class="literal">--relation</code>. This option suppresses that behavior.
</p></dd><dt><span class="term"><code class="option">--no-dependent-toast</code></span></dt><dd><p>
By default, if a table is checked, its toast table, if any, will also
be checked, even if it is not explicitly selected by an option
such as <code class="literal">--table</code> or <code class="literal">--relation</code>.
This option suppresses that behavior.
</p></dd><dt><span class="term"><code class="option">--no-strict-names</code></span></dt><dd><p>
By default, if an argument to <code class="literal">--database</code>,
<code class="literal">--table</code>, <code class="literal">--index</code>,
or <code class="literal">--relation</code> matches no objects, it is a fatal
error. This option downgrades that error to a warning.
</p></dd></dl></div><p>
</p><p>
The following command-line options control checking of tables:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--exclude-toast-pointers</code></span></dt><dd><p>
By default, whenever a toast pointer is encountered in a table,
a lookup is performed to ensure that it references apparently-valid
entries in the toast table. These checks can be quite slow, and this
option can be used to skip them.
</p></dd><dt><span class="term"><code class="option">--on-error-stop</code></span></dt><dd><p>
After reporting all corruptions on the first page of a table where
corruption is found, stop processing that table relation and move on
to the next table or index.
</p><p>
Note that index checking always stops after the first corrupt page.
This option only has meaning relative to table relations.
</p></dd><dt><span class="term"><code class="option">--skip=<em class="replaceable"><code>option</code></em></code></span></dt><dd><p>
If <code class="literal">all-frozen</code> is given, table corruption checks
will skip over pages in all tables that are marked as all frozen.
</p><p>
If <code class="literal">all-visible</code> is given, table corruption checks
will skip over pages in all tables that are marked as all visible.
</p><p>
By default, no pages are skipped. This can be specified as
<code class="literal">none</code>, but since this is the default, it need not be
mentioned.
</p></dd><dt><span class="term"><code class="option">--startblock=<em class="replaceable"><code>block</code></em></code></span></dt><dd><p>
Start checking at the specified block number. An error will occur if
the table relation being checked has fewer than this number of blocks.
This option does not apply to indexes, and is probably only useful
when checking a single table relation. See <code class="literal">--endblock</code>
for further caveats.
</p></dd><dt><span class="term"><code class="option">--endblock=<em class="replaceable"><code>block</code></em></code></span></dt><dd><p>
End checking at the specified block number. An error will occur if the
table relation being checked has fewer than this number of blocks.
This option does not apply to indexes, and is probably only useful when
checking a single table relation. If both a regular table and a toast
table are checked, this option will apply to both, but higher-numbered
toast blocks may still be accessed while validating toast pointers,
unless that is suppressed using
<code class="option">--exclude-toast-pointers</code>.
</p></dd></dl></div><p>
</p><p>
The following command-line options control checking of B-tree indexes:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--heapallindexed</code></span></dt><dd><p>
For each index checked, verify the presence of all heap tuples as index
tuples in the index using <a class="xref" href="amcheck.html" title="F.2. amcheck">amcheck</a>'s
<code class="option">heapallindexed</code> option.
</p></dd><dt><span class="term"><code class="option">--parent-check</code></span></dt><dd><p>
For each btree index checked, use <a class="xref" href="amcheck.html" title="F.2. amcheck">amcheck</a>'s
<code class="function">bt_index_parent_check</code> function, which performs
additional checks of parent/child relationships during index checking.
</p><p>
The default is to use <span class="application">amcheck</span>'s
<code class="function">bt_index_check</code> function, but note that use of the
<code class="option">--rootdescend</code> option implicitly selects
<code class="function">bt_index_parent_check</code>.
</p></dd><dt><span class="term"><code class="option">--rootdescend</code></span></dt><dd><p>
For each index checked, re-find tuples on the leaf level by performing a
new search from the root page for each tuple using
<a class="xref" href="amcheck.html" title="F.2. amcheck">amcheck</a>'s <code class="option">rootdescend</code> option.
</p><p>
Use of this option implicitly also selects the
<code class="option">--parent-check</code> option.
</p><p>
This form of verification was originally written to help in the
development of btree index features. It may be of limited use or even
of no use in helping detect the kinds of corruption that occur in
practice. It may also cause corruption checking to take considerably
longer and consume considerably more resources on the server.
</p></dd></dl></div><p>
</p><div class="warning"><h3 class="title">Warning</h3><p>
The extra checks performed against B-tree indexes when the
<code class="option">--parent-check</code> option or the
<code class="option">--rootdescend</code> option is specified require
relatively strong relation-level locks. These checks are the only
checks that will block concurrent data modification from
<code class="command">INSERT</code>, <code class="command">UPDATE</code>, and
<code class="command">DELETE</code> commands.
</p></div><p>
The following command-line options control the connection to the server:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-h <em class="replaceable"><code>hostname</code></em></code><br /></span><span class="term"><code class="option">--host=<em class="replaceable"><code>hostname</code></em></code></span></dt><dd><p>
Specifies the host name of the machine on which the server is running.
If the value begins with a slash, it is used as the directory for the
Unix domain socket.
</p></dd><dt><span class="term"><code class="option">-p <em class="replaceable"><code>port</code></em></code><br /></span><span class="term"><code class="option">--port=<em class="replaceable"><code>port</code></em></code></span></dt><dd><p>
Specifies the TCP port or local Unix domain socket file extension on
which the server is listening for connections.
</p></dd><dt><span class="term"><code class="option">-U</code><br /></span><span class="term"><code class="option">--username=<em class="replaceable"><code>username</code></em></code></span></dt><dd><p>
User name to connect as.
</p></dd><dt><span class="term"><code class="option">-w</code><br /></span><span class="term"><code class="option">--no-password</code></span></dt><dd><p>
Never issue a password prompt. If the server requires password
authentication and a password is not available by other means such as
a <code class="filename">.pgpass</code> file, the connection attempt will fail.
This option can be useful in batch jobs and scripts where no user is
present to enter a password.
</p></dd><dt><span class="term"><code class="option">-W</code><br /></span><span class="term"><code class="option">--password</code></span></dt><dd><p>
Force <span class="application">pg_amcheck</span> to prompt for a password
before connecting to a database.
</p><p>
This option is never essential, since
<span class="application">pg_amcheck</span> will automatically prompt for a
password if the server demands password authentication. However,
<span class="application">pg_amcheck</span> will waste a connection attempt
finding out that the server wants a password. In some cases it is
worth typing <code class="option">-W</code> to avoid the extra connection attempt.
</p></dd><dt><span class="term"><code class="option">--maintenance-db=<em class="replaceable"><code>dbname</code></em></code></span></dt><dd><p>
Specifies a database or
<a class="link" href="libpq-connect.html#LIBPQ-CONNSTRING" title="34.1.1. Connection Strings">connection string</a> to be
used to discover the list of databases to be checked. If neither
<code class="option">--all</code> nor any option including a database pattern is
used, no such connection is required and this option does nothing.
Otherwise, any connection string parameters other than
the database name which are included in the value for this option
will also be used when connecting to the databases
being checked. If this option is omitted, the default is
<code class="literal">postgres</code> or, if that fails,
<code class="literal">template1</code>.
</p></dd></dl></div><p>
</p><p>
Other options are also available:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-e</code><br /></span><span class="term"><code class="option">--echo</code></span></dt><dd><p>
Echo to stdout all SQL sent to the server.
</p></dd><dt><span class="term"><code class="option">-j <em class="replaceable"><code>num</code></em></code><br /></span><span class="term"><code class="option">--jobs=<em class="replaceable"><code>num</code></em></code></span></dt><dd><p>
Use <em class="replaceable"><code>num</code></em> concurrent connections to the server,
or one per object to be checked, whichever is less.
</p><p>
The default is to use a single connection.
</p></dd><dt><span class="term"><code class="option">-P</code><br /></span><span class="term"><code class="option">--progress</code></span></dt><dd><p>
Show progress information. Progress information includes the number
of relations for which checking has been completed, and the total
size of those relations. It also includes the total number of relations
that will eventually be checked, and the estimated size of those
relations.
</p></dd><dt><span class="term"><code class="option">-v</code><br /></span><span class="term"><code class="option">--verbose</code></span></dt><dd><p>
Print more messages. In particular, this will print a message for
each relation being checked, and will increase the level of detail
shown for server errors.
</p></dd><dt><span class="term"><code class="option">-V</code><br /></span><span class="term"><code class="option">--version</code></span></dt><dd><p>
Print the <span class="application">pg_amcheck</span> version and exit.
</p></dd><dt><span class="term"><code class="option">--install-missing</code><br /></span><span class="term"><code class="option">--install-missing=<em class="replaceable"><code>schema</code></em></code></span></dt><dd><p>
Install any missing extensions that are required to check the
database(s). If not yet installed, each extension's objects will be
installed into the given
<em class="replaceable"><code>schema</code></em>, or if not specified
into schema <code class="literal">pg_catalog</code>.
</p><p>
At present, the only required extension is <a class="xref" href="amcheck.html" title="F.2. amcheck">amcheck</a>.
</p></dd><dt><span class="term"><code class="option">-?</code><br /></span><span class="term"><code class="option">--help</code></span></dt><dd><p>
Show help about <span class="application">pg_amcheck</span> command line
arguments, and exit.
</p></dd></dl></div><p>
</p></div><div class="refsect1" id="id-1.9.4.9.7"><h2>Notes</h2><p>
<span class="application">pg_amcheck</span> is designed to work with
<span class="productname">PostgreSQL</span> 14.0 and later.
</p></div><div class="refsect1" id="id-1.9.4.9.8"><h2>See Also</h2><span class="simplelist"><a class="xref" href="amcheck.html" title="F.2. amcheck">amcheck</a></span></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="app-ecpg.html" title="ecpg">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="reference-client.html" title="PostgreSQL Client Applications">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="app-pgbasebackup.html" title="pg_basebackup">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span xmlns="http://www.w3.org/1999/xhtml" class="application">ecpg</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> <span xmlns="http://www.w3.org/1999/xhtml" class="application">pg_basebackup</span></td></tr></table></div></body></html>
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