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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>20.11. Client Connection Defaults</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="runtime-config-autovacuum.html" title="20.10. Automatic Vacuuming" /><link rel="next" href="runtime-config-locks.html" title="20.12. Lock Management" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">20.11. Client Connection Defaults</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="runtime-config-autovacuum.html" title="20.10. Automatic Vacuuming">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="runtime-config.html" title="Chapter 20. Server Configuration">Up</a></td><th width="60%" align="center">Chapter 20. Server Configuration</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.6 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="runtime-config-locks.html" title="20.12. Lock Management">Next</a></td></tr></table><hr /></div><div class="sect1" id="RUNTIME-CONFIG-CLIENT"><div class="titlepage"><div><div><h2 class="title" style="clear: both">20.11. Client Connection Defaults</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="runtime-config-client.html#RUNTIME-CONFIG-CLIENT-STATEMENT">20.11.1. Statement Behavior</a></span></dt><dt><span class="sect2"><a href="runtime-config-client.html#RUNTIME-CONFIG-CLIENT-FORMAT">20.11.2. Locale and Formatting</a></span></dt><dt><span class="sect2"><a href="runtime-config-client.html#RUNTIME-CONFIG-CLIENT-PRELOAD">20.11.3. Shared Library Preloading</a></span></dt><dt><span class="sect2"><a href="runtime-config-client.html#RUNTIME-CONFIG-CLIENT-OTHER">20.11.4. Other Defaults</a></span></dt></dl></div><div class="sect2" id="RUNTIME-CONFIG-CLIENT-STATEMENT"><div class="titlepage"><div><div><h3 class="title">20.11.1. Statement Behavior</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt id="GUC-CLIENT-MIN-MESSAGES"><span class="term"><code class="varname">client_min_messages</code> (<code class="type">enum</code>)
<a id="id-1.6.7.14.2.2.1.1.3" class="indexterm"></a>
</span></dt><dd><p>
Controls which
<a class="link" href="runtime-config-logging.html#RUNTIME-CONFIG-SEVERITY-LEVELS" title="Table 20.2. Message Severity Levels">message levels</a>
are sent to the client.
Valid values are <code class="literal">DEBUG5</code>,
<code class="literal">DEBUG4</code>, <code class="literal">DEBUG3</code>, <code class="literal">DEBUG2</code>,
<code class="literal">DEBUG1</code>, <code class="literal">LOG</code>, <code class="literal">NOTICE</code>,
<code class="literal">WARNING</code>, and <code class="literal">ERROR</code>.
Each level includes all the levels that follow it. The later the level,
the fewer messages are sent. The default is
<code class="literal">NOTICE</code>. Note that <code class="literal">LOG</code> has a different
rank here than in <a class="xref" href="runtime-config-logging.html#GUC-LOG-MIN-MESSAGES">log_min_messages</a>.
</p><p>
<code class="literal">INFO</code> level messages are always sent to the client.
</p></dd><dt id="GUC-SEARCH-PATH"><span class="term"><code class="varname">search_path</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.2.2.2.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.2.1.4" class="indexterm"></a>
</span></dt><dd><p>
This variable specifies the order in which schemas are searched
when an object (table, data type, function, etc.) is referenced by a
simple name with no schema specified. When there are objects of
identical names in different schemas, the one found first
in the search path is used. An object that is not in any of the
schemas in the search path can only be referenced by specifying
its containing schema with a qualified (dotted) name.
</p><p>
The value for <code class="varname">search_path</code> must be a comma-separated
list of schema names. Any name that is not an existing schema, or is
a schema for which the user does not have <code class="literal">USAGE</code>
permission, is silently ignored.
</p><p>
If one of the list items is the special name
<code class="literal">$user</code>, then the schema having the name returned by
<code class="function">CURRENT_USER</code> is substituted, if there is such a schema
and the user has <code class="literal">USAGE</code> permission for it.
(If not, <code class="literal">$user</code> is ignored.)
</p><p>
The system catalog schema, <code class="literal">pg_catalog</code>, is always
searched, whether it is mentioned in the path or not. If it is
mentioned in the path then it will be searched in the specified
order. If <code class="literal">pg_catalog</code> is not in the path then it will
be searched <span class="emphasis"><em>before</em></span> searching any of the path items.
</p><p>
Likewise, the current session's temporary-table schema,
<code class="literal">pg_temp_<em class="replaceable"><code>nnn</code></em></code>, is always searched if it
exists. It can be explicitly listed in the path by using the
alias <code class="literal">pg_temp</code><a id="id-1.6.7.14.2.2.2.2.5.3" class="indexterm"></a>. If it is not listed in the path then
it is searched first (even before <code class="literal">pg_catalog</code>). However,
the temporary schema is only searched for relation (table, view,
sequence, etc.) and data type names. It is never searched for
function or operator names.
</p><p>
When objects are created without specifying a particular target
schema, they will be placed in the first valid schema named in
<code class="varname">search_path</code>. An error is reported if the search
path is empty.
</p><p>
The default value for this parameter is
<code class="literal">"$user", public</code>.
This setting supports shared use of a database (where no users
have private schemas, and all share use of <code class="literal">public</code>),
private per-user schemas, and combinations of these. Other
effects can be obtained by altering the default search path
setting, either globally or per-user.
</p><p>
For more information on schema handling, see
<a class="xref" href="ddl-schemas.html" title="5.9. Schemas">Section 5.9</a>. In particular, the default
configuration is suitable only when the database has a single user or
a few mutually-trusting users.
</p><p>
The current effective value of the search path can be examined
via the <acronym class="acronym">SQL</acronym> function
<code class="function">current_schemas</code>
(see <a class="xref" href="functions-info.html" title="9.26. System Information Functions and Operators">Section 9.26</a>).
This is not quite the same as
examining the value of <code class="varname">search_path</code>, since
<code class="function">current_schemas</code> shows how the items
appearing in <code class="varname">search_path</code> were resolved.
</p></dd><dt id="GUC-ROW-SECURITY"><span class="term"><code class="varname">row_security</code> (<code class="type">boolean</code>)
<a id="id-1.6.7.14.2.2.3.1.3" class="indexterm"></a>
</span></dt><dd><p>
This variable controls whether to raise an error in lieu of applying a
row security policy. When set to <code class="literal">on</code>, policies apply
normally. When set to <code class="literal">off</code>, queries fail which would
otherwise apply at least one policy. The default is <code class="literal">on</code>.
Change to <code class="literal">off</code> where limited row visibility could cause
incorrect results; for example, <span class="application">pg_dump</span> makes that
change by default. This variable has no effect on roles which bypass
every row security policy, to wit, superusers and roles with
the <code class="literal">BYPASSRLS</code> attribute.
</p><p>
For more information on row security policies,
see <a class="xref" href="sql-createpolicy.html" title="CREATE POLICY"><span class="refentrytitle">CREATE POLICY</span></a>.
</p></dd><dt id="GUC-DEFAULT-TABLE-ACCESS-METHOD"><span class="term"><code class="varname">default_table_access_method</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.2.2.4.1.3" class="indexterm"></a>
</span></dt><dd><p>
This parameter specifies the default table access method to use when
creating tables or materialized views if the <code class="command">CREATE</code>
command does not explicitly specify an access method, or when
<code class="command">SELECT ... INTO</code> is used, which does not allow
specifying a table access method. The default is <code class="literal">heap</code>.
</p></dd><dt id="GUC-DEFAULT-TABLESPACE"><span class="term"><code class="varname">default_tablespace</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.2.2.5.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.5.1.4" class="indexterm"></a>
</span></dt><dd><p>
This variable specifies the default tablespace in which to create
objects (tables and indexes) when a <code class="command">CREATE</code> command does
not explicitly specify a tablespace.
</p><p>
The value is either the name of a tablespace, or an empty string
to specify using the default tablespace of the current database.
If the value does not match the name of any existing tablespace,
<span class="productname">PostgreSQL</span> will automatically use the default
tablespace of the current database. If a nondefault tablespace
is specified, the user must have <code class="literal">CREATE</code> privilege
for it, or creation attempts will fail.
</p><p>
This variable is not used for temporary tables; for them,
<a class="xref" href="runtime-config-client.html#GUC-TEMP-TABLESPACES">temp_tablespaces</a> is consulted instead.
</p><p>
This variable is also not used when creating databases.
By default, a new database inherits its tablespace setting from
the template database it is copied from.
</p><p>
If this parameter is set to a value other than the empty string
when a partitioned table is created, the partitioned table's
tablespace will be set to that value, which will be used as
the default tablespace for partitions created in the future,
even if <code class="varname">default_tablespace</code> has changed since then.
</p><p>
For more information on tablespaces,
see <a class="xref" href="manage-ag-tablespaces.html" title="23.6. Tablespaces">Section 23.6</a>.
</p></dd><dt id="GUC-DEFAULT-TOAST-COMPRESSION"><span class="term"><code class="varname">default_toast_compression</code> (<code class="type">enum</code>)
<a id="id-1.6.7.14.2.2.6.1.3" class="indexterm"></a>
</span></dt><dd><p>
This variable sets the default
<a class="link" href="storage-toast.html" title="73.2. TOAST">TOAST</a>
compression method for values of compressible columns.
(This can be overridden for individual columns by setting
the <code class="literal">COMPRESSION</code> column option in
<code class="command">CREATE TABLE</code> or
<code class="command">ALTER TABLE</code>.)
The supported compression methods are <code class="literal">pglz</code> and
(if <span class="productname">PostgreSQL</span> was compiled with
<code class="option">--with-lz4</code>) <code class="literal">lz4</code>.
The default is <code class="literal">pglz</code>.
</p></dd><dt id="GUC-TEMP-TABLESPACES"><span class="term"><code class="varname">temp_tablespaces</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.2.2.7.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.7.1.4" class="indexterm"></a>
</span></dt><dd><p>
This variable specifies tablespaces in which to create temporary
objects (temp tables and indexes on temp tables) when a
<code class="command">CREATE</code> command does not explicitly specify a tablespace.
Temporary files for purposes such as sorting large data sets
are also created in these tablespaces.
</p><p>
The value is a list of names of tablespaces. When there is more than
one name in the list, <span class="productname">PostgreSQL</span> chooses a random
member of the list each time a temporary object is to be created;
except that within a transaction, successively created temporary
objects are placed in successive tablespaces from the list.
If the selected element of the list is an empty string,
<span class="productname">PostgreSQL</span> will automatically use the default
tablespace of the current database instead.
</p><p>
When <code class="varname">temp_tablespaces</code> is set interactively, specifying a
nonexistent tablespace is an error, as is specifying a tablespace for
which the user does not have <code class="literal">CREATE</code> privilege. However,
when using a previously set value, nonexistent tablespaces are
ignored, as are tablespaces for which the user lacks
<code class="literal">CREATE</code> privilege. In particular, this rule applies when
using a value set in <code class="filename">postgresql.conf</code>.
</p><p>
The default value is an empty string, which results in all temporary
objects being created in the default tablespace of the current
database.
</p><p>
See also <a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TABLESPACE">default_tablespace</a>.
</p></dd><dt id="GUC-CHECK-FUNCTION-BODIES"><span class="term"><code class="varname">check_function_bodies</code> (<code class="type">boolean</code>)
<a id="id-1.6.7.14.2.2.8.1.3" class="indexterm"></a>
</span></dt><dd><p>
This parameter is normally on. When set to <code class="literal">off</code>, it
disables validation of the routine body string during <a class="xref" href="sql-createfunction.html" title="CREATE FUNCTION"><span class="refentrytitle">CREATE FUNCTION</span></a> and <a class="xref" href="sql-createprocedure.html" title="CREATE PROCEDURE"><span class="refentrytitle">CREATE PROCEDURE</span></a>. Disabling validation avoids side
effects of the validation process, in particular preventing false
positives due to problems such as forward references.
Set this parameter
to <code class="literal">off</code> before loading functions on behalf of other
users; <span class="application">pg_dump</span> does so automatically.
</p></dd><dt id="GUC-DEFAULT-TRANSACTION-ISOLATION"><span class="term"><code class="varname">default_transaction_isolation</code> (<code class="type">enum</code>)
<a id="id-1.6.7.14.2.2.9.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.9.1.4" class="indexterm"></a>
</span></dt><dd><p>
Each SQL transaction has an isolation level, which can be
either <span class="quote">“<span class="quote">read uncommitted</span>”</span>, <span class="quote">“<span class="quote">read
committed</span>”</span>, <span class="quote">“<span class="quote">repeatable read</span>”</span>, or
<span class="quote">“<span class="quote">serializable</span>”</span>. This parameter controls the
default isolation level of each new transaction. The default
is <span class="quote">“<span class="quote">read committed</span>”</span>.
</p><p>
Consult <a class="xref" href="mvcc.html" title="Chapter 13. Concurrency Control">Chapter 13</a> and <a class="xref" href="sql-set-transaction.html" title="SET TRANSACTION"><span class="refentrytitle">SET TRANSACTION</span></a> for more information.
</p></dd><dt id="GUC-DEFAULT-TRANSACTION-READ-ONLY"><span class="term"><code class="varname">default_transaction_read_only</code> (<code class="type">boolean</code>)
<a id="id-1.6.7.14.2.2.10.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.10.1.4" class="indexterm"></a>
</span></dt><dd><p>
A read-only SQL transaction cannot alter non-temporary tables.
This parameter controls the default read-only status of each new
transaction. The default is <code class="literal">off</code> (read/write).
</p><p>
Consult <a class="xref" href="sql-set-transaction.html" title="SET TRANSACTION"><span class="refentrytitle">SET TRANSACTION</span></a> for more information.
</p></dd><dt id="GUC-DEFAULT-TRANSACTION-DEFERRABLE"><span class="term"><code class="varname">default_transaction_deferrable</code> (<code class="type">boolean</code>)
<a id="id-1.6.7.14.2.2.11.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.11.1.4" class="indexterm"></a>
</span></dt><dd><p>
When running at the <code class="literal">serializable</code> isolation level,
a deferrable read-only SQL transaction may be delayed before
it is allowed to proceed. However, once it begins executing
it does not incur any of the overhead required to ensure
serializability; so serialization code will have no reason to
force it to abort because of concurrent updates, making this
option suitable for long-running read-only transactions.
</p><p>
This parameter controls the default deferrable status of each
new transaction. It currently has no effect on read-write
transactions or those operating at isolation levels lower
than <code class="literal">serializable</code>. The default is <code class="literal">off</code>.
</p><p>
Consult <a class="xref" href="sql-set-transaction.html" title="SET TRANSACTION"><span class="refentrytitle">SET TRANSACTION</span></a> for more information.
</p></dd><dt id="GUC-TRANSACTION-ISOLATION"><span class="term"><code class="varname">transaction_isolation</code> (<code class="type">enum</code>)
<a id="id-1.6.7.14.2.2.12.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.12.1.4" class="indexterm"></a>
</span></dt><dd><p>
This parameter reflects the current transaction's isolation level.
At the beginning of each transaction, it is set to the current value
of <a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TRANSACTION-ISOLATION">default_transaction_isolation</a>.
Any subsequent attempt to change it is equivalent to a <a class="xref" href="sql-set-transaction.html" title="SET TRANSACTION"><span class="refentrytitle">SET TRANSACTION</span></a> command.
</p></dd><dt id="GUC-TRANSACTION-READ-ONLY"><span class="term"><code class="varname">transaction_read_only</code> (<code class="type">boolean</code>)
<a id="id-1.6.7.14.2.2.13.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.13.1.4" class="indexterm"></a>
</span></dt><dd><p>
This parameter reflects the current transaction's read-only status.
At the beginning of each transaction, it is set to the current value
of <a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TRANSACTION-READ-ONLY">default_transaction_read_only</a>.
Any subsequent attempt to change it is equivalent to a <a class="xref" href="sql-set-transaction.html" title="SET TRANSACTION"><span class="refentrytitle">SET TRANSACTION</span></a> command.
</p></dd><dt id="GUC-TRANSACTION-DEFERRABLE"><span class="term"><code class="varname">transaction_deferrable</code> (<code class="type">boolean</code>)
<a id="id-1.6.7.14.2.2.14.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.14.1.4" class="indexterm"></a>
</span></dt><dd><p>
This parameter reflects the current transaction's deferrability status.
At the beginning of each transaction, it is set to the current value
of <a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TRANSACTION-DEFERRABLE">default_transaction_deferrable</a>.
Any subsequent attempt to change it is equivalent to a <a class="xref" href="sql-set-transaction.html" title="SET TRANSACTION"><span class="refentrytitle">SET TRANSACTION</span></a> command.
</p></dd><dt id="GUC-SESSION-REPLICATION-ROLE"><span class="term"><code class="varname">session_replication_role</code> (<code class="type">enum</code>)
<a id="id-1.6.7.14.2.2.15.1.3" class="indexterm"></a>
</span></dt><dd><p>
Controls firing of replication-related triggers and rules for the
current session.
Possible values are <code class="literal">origin</code> (the default),
<code class="literal">replica</code> and <code class="literal">local</code>.
Setting this parameter results in discarding any previously cached
query plans.
Only superusers and users with the appropriate <code class="literal">SET</code>
privilege can change this setting.
</p><p>
The intended use of this setting is that logical replication systems
set it to <code class="literal">replica</code> when they are applying replicated
changes. The effect of that will be that triggers and rules (that
have not been altered from their default configuration) will not fire
on the replica. See the <a class="link" href="sql-altertable.html" title="ALTER TABLE"><code class="command">ALTER TABLE</code></a> clauses
<code class="literal">ENABLE TRIGGER</code> and <code class="literal">ENABLE RULE</code>
for more information.
</p><p>
PostgreSQL treats the settings <code class="literal">origin</code> and
<code class="literal">local</code> the same internally. Third-party replication
systems may use these two values for their internal purposes, for
example using <code class="literal">local</code> to designate a session whose
changes should not be replicated.
</p><p>
Since foreign keys are implemented as triggers, setting this parameter
to <code class="literal">replica</code> also disables all foreign key checks,
which can leave data in an inconsistent state if improperly used.
</p></dd><dt id="GUC-STATEMENT-TIMEOUT"><span class="term"><code class="varname">statement_timeout</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.16.1.3" class="indexterm"></a>
</span></dt><dd><p>
Abort any statement that takes more than the specified amount of time.
If <code class="varname">log_min_error_statement</code> is set
to <code class="literal">ERROR</code> or lower, the statement that timed out
will also be logged.
If this value is specified without units, it is taken as milliseconds.
A value of zero (the default) disables the timeout.
</p><p>
The timeout is measured from the time a command arrives at the
server until it is completed by the server. If multiple SQL
statements appear in a single simple-Query message, the timeout
is applied to each statement separately.
(<span class="productname">PostgreSQL</span> versions before 13 usually
treated the timeout as applying to the whole query string.)
In extended query protocol, the timeout starts running when any
query-related message (Parse, Bind, Execute, Describe) arrives, and
it is canceled by completion of an Execute or Sync message.
</p><p>
Setting <code class="varname">statement_timeout</code> in
<code class="filename">postgresql.conf</code> is not recommended because it would
affect all sessions.
</p></dd><dt id="GUC-LOCK-TIMEOUT"><span class="term"><code class="varname">lock_timeout</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.17.1.3" class="indexterm"></a>
</span></dt><dd><p>
Abort any statement that waits longer than the specified amount of
time while attempting to acquire a lock on a table, index,
row, or other database object. The time limit applies separately to
each lock acquisition attempt. The limit applies both to explicit
locking requests (such as <code class="command">LOCK TABLE</code>, or <code class="command">SELECT
FOR UPDATE</code> without <code class="literal">NOWAIT</code>) and to implicitly-acquired
locks.
If this value is specified without units, it is taken as milliseconds.
A value of zero (the default) disables the timeout.
</p><p>
Unlike <code class="varname">statement_timeout</code>, this timeout can only occur
while waiting for locks. Note that if <code class="varname">statement_timeout</code>
is nonzero, it is rather pointless to set <code class="varname">lock_timeout</code> to
the same or larger value, since the statement timeout would always
trigger first. If <code class="varname">log_min_error_statement</code> is set to
<code class="literal">ERROR</code> or lower, the statement that timed out will be
logged.
</p><p>
Setting <code class="varname">lock_timeout</code> in
<code class="filename">postgresql.conf</code> is not recommended because it would
affect all sessions.
</p></dd><dt id="GUC-IDLE-IN-TRANSACTION-SESSION-TIMEOUT"><span class="term"><code class="varname">idle_in_transaction_session_timeout</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.18.1.3" class="indexterm"></a>
</span></dt><dd><p>
Terminate any session that has been idle (that is, waiting for a
client query) within an open transaction for longer than the
specified amount of time.
If this value is specified without units, it is taken as milliseconds.
A value of zero (the default) disables the timeout.
</p><p>
This option can be used to ensure that idle sessions do not hold
locks for an unreasonable amount of time. Even when no significant
locks are held, an open transaction prevents vacuuming away
recently-dead tuples that may be visible only to this transaction;
so remaining idle for a long time can contribute to table bloat.
See <a class="xref" href="routine-vacuuming.html" title="25.1. Routine Vacuuming">Section 25.1</a> for more details.
</p></dd><dt id="GUC-IDLE-SESSION-TIMEOUT"><span class="term"><code class="varname">idle_session_timeout</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.19.1.3" class="indexterm"></a>
</span></dt><dd><p>
Terminate any session that has been idle (that is, waiting for a
client query), but not within an open transaction, for longer than
the specified amount of time.
If this value is specified without units, it is taken as milliseconds.
A value of zero (the default) disables the timeout.
</p><p>
Unlike the case with an open transaction, an idle session without a
transaction imposes no large costs on the server, so there is less
need to enable this timeout
than <code class="varname">idle_in_transaction_session_timeout</code>.
</p><p>
Be wary of enforcing this timeout on connections made through
connection-pooling software or other middleware, as such a layer
may not react well to unexpected connection closure. It may be
helpful to enable this timeout only for interactive sessions,
perhaps by applying it only to particular users.
</p></dd><dt id="GUC-VACUUM-FREEZE-TABLE-AGE"><span class="term"><code class="varname">vacuum_freeze_table_age</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.20.1.3" class="indexterm"></a>
</span></dt><dd><p>
<code class="command">VACUUM</code> performs an aggressive scan if the table's
<code class="structname">pg_class</code>.<code class="structfield">relfrozenxid</code> field has reached
the age specified by this setting. An aggressive scan differs from
a regular <code class="command">VACUUM</code> in that it visits every page that might
contain unfrozen XIDs or MXIDs, not just those that might contain dead
tuples. The default is 150 million transactions. Although users can
set this value anywhere from zero to two billion, <code class="command">VACUUM</code>
will silently limit the effective value to 95% of
<a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-FREEZE-MAX-AGE">autovacuum_freeze_max_age</a>, so that a
periodic manual <code class="command">VACUUM</code> has a chance to run before an
anti-wraparound autovacuum is launched for the table. For more
information see
<a class="xref" href="routine-vacuuming.html#VACUUM-FOR-WRAPAROUND" title="25.1.5. Preventing Transaction ID Wraparound Failures">Section 25.1.5</a>.
</p></dd><dt id="GUC-VACUUM-FREEZE-MIN-AGE"><span class="term"><code class="varname">vacuum_freeze_min_age</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.21.1.3" class="indexterm"></a>
</span></dt><dd><p>
Specifies the cutoff age (in transactions) that <code class="command">VACUUM</code>
should use to decide whether to freeze row versions
while scanning a table.
The default is 50 million transactions. Although
users can set this value anywhere from zero to one billion,
<code class="command">VACUUM</code> will silently limit the effective value to half
the value of <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-FREEZE-MAX-AGE">autovacuum_freeze_max_age</a>, so
that there is not an unreasonably short time between forced
autovacuums. For more information see <a class="xref" href="routine-vacuuming.html#VACUUM-FOR-WRAPAROUND" title="25.1.5. Preventing Transaction ID Wraparound Failures">Section 25.1.5</a>.
</p></dd><dt id="GUC-VACUUM-FAILSAFE-AGE"><span class="term"><code class="varname">vacuum_failsafe_age</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.22.1.3" class="indexterm"></a>
</span></dt><dd><p>
Specifies the maximum age (in transactions) that a table's
<code class="structname">pg_class</code>.<code class="structfield">relfrozenxid</code>
field can attain before <code class="command">VACUUM</code> takes
extraordinary measures to avoid system-wide transaction ID
wraparound failure. This is <code class="command">VACUUM</code>'s
strategy of last resort. The failsafe typically triggers
when an autovacuum to prevent transaction ID wraparound has
already been running for some time, though it's possible for
the failsafe to trigger during any <code class="command">VACUUM</code>.
</p><p>
When the failsafe is triggered, any cost-based delay that is
in effect will no longer be applied, and further non-essential
maintenance tasks (such as index vacuuming) are bypassed.
</p><p>
The default is 1.6 billion transactions. Although users can
set this value anywhere from zero to 2.1 billion,
<code class="command">VACUUM</code> will silently adjust the effective
value to no less than 105% of <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-FREEZE-MAX-AGE">autovacuum_freeze_max_age</a>.
</p></dd><dt id="GUC-VACUUM-MULTIXACT-FREEZE-TABLE-AGE"><span class="term"><code class="varname">vacuum_multixact_freeze_table_age</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.23.1.3" class="indexterm"></a>
</span></dt><dd><p>
<code class="command">VACUUM</code> performs an aggressive scan if the table's
<code class="structname">pg_class</code>.<code class="structfield">relminmxid</code> field has reached
the age specified by this setting. An aggressive scan differs from
a regular <code class="command">VACUUM</code> in that it visits every page that might
contain unfrozen XIDs or MXIDs, not just those that might contain dead
tuples. The default is 150 million multixacts.
Although users can set this value anywhere from zero to two billion,
<code class="command">VACUUM</code> will silently limit the effective value to 95% of
<a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-MULTIXACT-FREEZE-MAX-AGE">autovacuum_multixact_freeze_max_age</a>, so that a
periodic manual <code class="command">VACUUM</code> has a chance to run before an
anti-wraparound is launched for the table.
For more information see <a class="xref" href="routine-vacuuming.html#VACUUM-FOR-MULTIXACT-WRAPAROUND" title="25.1.5.1. Multixacts and Wraparound">Section 25.1.5.1</a>.
</p></dd><dt id="GUC-VACUUM-MULTIXACT-FREEZE-MIN-AGE"><span class="term"><code class="varname">vacuum_multixact_freeze_min_age</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.24.1.3" class="indexterm"></a>
</span></dt><dd><p>
Specifies the cutoff age (in multixacts) that <code class="command">VACUUM</code>
should use to decide whether to replace multixact IDs with a newer
transaction ID or multixact ID while scanning a table. The default
is 5 million multixacts.
Although users can set this value anywhere from zero to one billion,
<code class="command">VACUUM</code> will silently limit the effective value to half
the value of <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-MULTIXACT-FREEZE-MAX-AGE">autovacuum_multixact_freeze_max_age</a>,
so that there is not an unreasonably short time between forced
autovacuums.
For more information see <a class="xref" href="routine-vacuuming.html#VACUUM-FOR-MULTIXACT-WRAPAROUND" title="25.1.5.1. Multixacts and Wraparound">Section 25.1.5.1</a>.
</p></dd><dt id="GUC-VACUUM-MULTIXACT-FAILSAFE-AGE"><span class="term"><code class="varname">vacuum_multixact_failsafe_age</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.25.1.3" class="indexterm"></a>
</span></dt><dd><p>
Specifies the maximum age (in multixacts) that a table's
<code class="structname">pg_class</code>.<code class="structfield">relminmxid</code>
field can attain before <code class="command">VACUUM</code> takes
extraordinary measures to avoid system-wide multixact ID
wraparound failure. This is <code class="command">VACUUM</code>'s
strategy of last resort. The failsafe typically triggers when
an autovacuum to prevent transaction ID wraparound has already
been running for some time, though it's possible for the
failsafe to trigger during any <code class="command">VACUUM</code>.
</p><p>
When the failsafe is triggered, any cost-based delay that is
in effect will no longer be applied, and further non-essential
maintenance tasks (such as index vacuuming) are bypassed.
</p><p>
The default is 1.6 billion multixacts. Although users can set
this value anywhere from zero to 2.1 billion,
<code class="command">VACUUM</code> will silently adjust the effective
value to no less than 105% of <a class="xref" href="runtime-config-autovacuum.html#GUC-AUTOVACUUM-MULTIXACT-FREEZE-MAX-AGE">autovacuum_multixact_freeze_max_age</a>.
</p></dd><dt id="GUC-BYTEA-OUTPUT"><span class="term"><code class="varname">bytea_output</code> (<code class="type">enum</code>)
<a id="id-1.6.7.14.2.2.26.1.3" class="indexterm"></a>
</span></dt><dd><p>
Sets the output format for values of type <code class="type">bytea</code>.
Valid values are <code class="literal">hex</code> (the default)
and <code class="literal">escape</code> (the traditional PostgreSQL
format). See <a class="xref" href="datatype-binary.html" title="8.4. Binary Data Types">Section 8.4</a> for more
information. The <code class="type">bytea</code> type always
accepts both formats on input, regardless of this setting.
</p></dd><dt id="GUC-XMLBINARY"><span class="term"><code class="varname">xmlbinary</code> (<code class="type">enum</code>)
<a id="id-1.6.7.14.2.2.27.1.3" class="indexterm"></a>
</span></dt><dd><p>
Sets how binary values are to be encoded in XML. This applies
for example when <code class="type">bytea</code> values are converted to
XML by the functions <code class="function">xmlelement</code> or
<code class="function">xmlforest</code>. Possible values are
<code class="literal">base64</code> and <code class="literal">hex</code>, which
are both defined in the XML Schema standard. The default is
<code class="literal">base64</code>. For further information about
XML-related functions, see <a class="xref" href="functions-xml.html" title="9.15. XML Functions">Section 9.15</a>.
</p><p>
The actual choice here is mostly a matter of taste,
constrained only by possible restrictions in client
applications. Both methods support all possible values,
although the hex encoding will be somewhat larger than the
base64 encoding.
</p></dd><dt id="GUC-XMLOPTION"><span class="term"><code class="varname">xmloption</code> (<code class="type">enum</code>)
<a id="id-1.6.7.14.2.2.28.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.28.1.4" class="indexterm"></a>
<a id="id-1.6.7.14.2.2.28.1.5" class="indexterm"></a>
</span></dt><dd><p>
Sets whether <code class="literal">DOCUMENT</code> or
<code class="literal">CONTENT</code> is implicit when converting between
XML and character string values. See <a class="xref" href="datatype-xml.html" title="8.13. XML Type">Section 8.13</a> for a description of this. Valid
values are <code class="literal">DOCUMENT</code> and
<code class="literal">CONTENT</code>. The default is
<code class="literal">CONTENT</code>.
</p><p>
According to the SQL standard, the command to set this option is
</p><pre class="synopsis">
SET XML OPTION { DOCUMENT | CONTENT };
</pre><p>
This syntax is also available in PostgreSQL.
</p></dd><dt id="GUC-GIN-PENDING-LIST-LIMIT"><span class="term"><code class="varname">gin_pending_list_limit</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.2.2.29.1.3" class="indexterm"></a>
</span></dt><dd><p>
Sets the maximum size of a GIN index's pending list, which is used
when <code class="literal">fastupdate</code> is enabled. If the list grows
larger than this maximum size, it is cleaned up by moving
the entries in it to the index's main GIN data structure in bulk.
If this value is specified without units, it is taken as kilobytes.
The default is four megabytes (<code class="literal">4MB</code>). This setting
can be overridden for individual GIN indexes by changing
index storage parameters.
See <a class="xref" href="gin-implementation.html#GIN-FAST-UPDATE" title="70.4.1. GIN Fast Update Technique">Section 70.4.1</a> and <a class="xref" href="gin-tips.html" title="70.5. GIN Tips and Tricks">Section 70.5</a>
for more information.
</p></dd></dl></div></div><div class="sect2" id="RUNTIME-CONFIG-CLIENT-FORMAT"><div class="titlepage"><div><div><h3 class="title">20.11.2. Locale and Formatting</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt id="GUC-DATESTYLE"><span class="term"><code class="varname">DateStyle</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.3.2.1.1.3" class="indexterm"></a>
</span></dt><dd><p>
Sets the display format for date and time values, as well as the
rules for interpreting ambiguous date input values. For
historical reasons, this variable contains two independent
components: the output format specification (<code class="literal">ISO</code>,
<code class="literal">Postgres</code>, <code class="literal">SQL</code>, or <code class="literal">German</code>)
and the input/output specification for year/month/day ordering
(<code class="literal">DMY</code>, <code class="literal">MDY</code>, or <code class="literal">YMD</code>). These
can be set separately or together. The keywords <code class="literal">Euro</code>
and <code class="literal">European</code> are synonyms for <code class="literal">DMY</code>; the
keywords <code class="literal">US</code>, <code class="literal">NonEuro</code>, and
<code class="literal">NonEuropean</code> are synonyms for <code class="literal">MDY</code>. See
<a class="xref" href="datatype-datetime.html" title="8.5. Date/Time Types">Section 8.5</a> for more information. The
built-in default is <code class="literal">ISO, MDY</code>, but
<span class="application">initdb</span> will initialize the
configuration file with a setting that corresponds to the
behavior of the chosen <code class="varname">lc_time</code> locale.
</p></dd><dt id="GUC-INTERVALSTYLE"><span class="term"><code class="varname">IntervalStyle</code> (<code class="type">enum</code>)
<a id="id-1.6.7.14.3.2.2.1.3" class="indexterm"></a>
</span></dt><dd><p>
Sets the display format for interval values.
The value <code class="literal">sql_standard</code> will produce
output matching <acronym class="acronym">SQL</acronym> standard interval literals.
The value <code class="literal">postgres</code> (which is the default) will produce
output matching <span class="productname">PostgreSQL</span> releases prior to 8.4
when the <a class="xref" href="runtime-config-client.html#GUC-DATESTYLE">DateStyle</a>
parameter was set to <code class="literal">ISO</code>.
The value <code class="literal">postgres_verbose</code> will produce output
matching <span class="productname">PostgreSQL</span> releases prior to 8.4
when the <code class="varname">DateStyle</code>
parameter was set to non-<code class="literal">ISO</code> output.
The value <code class="literal">iso_8601</code> will produce output matching the time
interval <span class="quote">“<span class="quote">format with designators</span>”</span> defined in section
4.4.3.2 of ISO 8601.
</p><p>
The <code class="varname">IntervalStyle</code> parameter also affects the
interpretation of ambiguous interval input. See
<a class="xref" href="datatype-datetime.html#DATATYPE-INTERVAL-INPUT" title="8.5.4. Interval Input">Section 8.5.4</a> for more information.
</p></dd><dt id="GUC-TIMEZONE"><span class="term"><code class="varname">TimeZone</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.3.2.3.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.3.2.3.1.4" class="indexterm"></a>
</span></dt><dd><p>
Sets the time zone for displaying and interpreting time stamps.
The built-in default is <code class="literal">GMT</code>, but that is typically
overridden in <code class="filename">postgresql.conf</code>; <span class="application">initdb</span>
will install a setting there corresponding to its system environment.
See <a class="xref" href="datatype-datetime.html#DATATYPE-TIMEZONES" title="8.5.3. Time Zones">Section 8.5.3</a> for more information.
</p></dd><dt id="GUC-TIMEZONE-ABBREVIATIONS"><span class="term"><code class="varname">timezone_abbreviations</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.3.2.4.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.3.2.4.1.4" class="indexterm"></a>
</span></dt><dd><p>
Sets the collection of time zone abbreviations that will be accepted
by the server for datetime input. The default is <code class="literal">'Default'</code>,
which is a collection that works in most of the world; there are
also <code class="literal">'Australia'</code> and <code class="literal">'India'</code>,
and other collections can be defined for a particular installation.
See <a class="xref" href="datetime-config-files.html" title="B.4. Date/Time Configuration Files">Section B.4</a> for more information.
</p></dd><dt id="GUC-EXTRA-FLOAT-DIGITS"><span class="term"><code class="varname">extra_float_digits</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.3.2.5.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.3.2.5.1.4" class="indexterm"></a>
<a id="id-1.6.7.14.3.2.5.1.5" class="indexterm"></a>
</span></dt><dd><p>
This parameter adjusts the number of digits used for textual output of
floating-point values, including <code class="type">float4</code>, <code class="type">float8</code>,
and geometric data types.
</p><p>
If the value is 1 (the default) or above, float values are output in
shortest-precise format; see <a class="xref" href="datatype-numeric.html#DATATYPE-FLOAT" title="8.1.3. Floating-Point Types">Section 8.1.3</a>. The
actual number of digits generated depends only on the value being
output, not on the value of this parameter. At most 17 digits are
required for <code class="type">float8</code> values, and 9 for <code class="type">float4</code>
values. This format is both fast and precise, preserving the original
binary float value exactly when correctly read. For historical
compatibility, values up to 3 are permitted.
</p><p>
If the value is zero or negative, then the output is rounded to a
given decimal precision. The precision used is the standard number of
digits for the type (<code class="literal">FLT_DIG</code>
or <code class="literal">DBL_DIG</code> as appropriate) reduced according to the
value of this parameter. (For example, specifying -1 will cause
<code class="type">float4</code> values to be output rounded to 5 significant
digits, and <code class="type">float8</code> values
rounded to 14 digits.) This format is slower and does not preserve all
the bits of the binary float value, but may be more human-readable.
</p><div class="note"><h3 class="title">Note</h3><p>
The meaning of this parameter, and its default value, changed
in <span class="productname">PostgreSQL</span> 12;
see <a class="xref" href="datatype-numeric.html#DATATYPE-FLOAT" title="8.1.3. Floating-Point Types">Section 8.1.3</a> for further discussion.
</p></div></dd><dt id="GUC-CLIENT-ENCODING"><span class="term"><code class="varname">client_encoding</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.3.2.6.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.3.2.6.1.4" class="indexterm"></a>
</span></dt><dd><p>
Sets the client-side encoding (character set).
The default is to use the database encoding.
The character sets supported by the <span class="productname">PostgreSQL</span>
server are described in <a class="xref" href="multibyte.html#MULTIBYTE-CHARSET-SUPPORTED" title="24.3.1. Supported Character Sets">Section 24.3.1</a>.
</p></dd><dt id="GUC-LC-MESSAGES"><span class="term"><code class="varname">lc_messages</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.3.2.7.1.3" class="indexterm"></a>
</span></dt><dd><p>
Sets the language in which messages are displayed. Acceptable
values are system-dependent; see <a class="xref" href="locale.html" title="24.1. Locale Support">Section 24.1</a> for
more information. If this variable is set to the empty string
(which is the default) then the value is inherited from the
execution environment of the server in a system-dependent way.
</p><p>
On some systems, this locale category does not exist. Setting
this variable will still work, but there will be no effect.
Also, there is a chance that no translated messages for the
desired language exist. In that case you will continue to see
the English messages.
</p><p>
Only superusers and users with the appropriate <code class="literal">SET</code>
privilege can change this setting.
</p></dd><dt id="GUC-LC-MONETARY"><span class="term"><code class="varname">lc_monetary</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.3.2.8.1.3" class="indexterm"></a>
</span></dt><dd><p>
Sets the locale to use for formatting monetary amounts, for
example with the <code class="function">to_char</code> family of
functions. Acceptable values are system-dependent; see <a class="xref" href="locale.html" title="24.1. Locale Support">Section 24.1</a> for more information. If this variable is
set to the empty string (which is the default) then the value
is inherited from the execution environment of the server in a
system-dependent way.
</p></dd><dt id="GUC-LC-NUMERIC"><span class="term"><code class="varname">lc_numeric</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.3.2.9.1.3" class="indexterm"></a>
</span></dt><dd><p>
Sets the locale to use for formatting numbers, for example
with the <code class="function">to_char</code> family of
functions. Acceptable values are system-dependent; see <a class="xref" href="locale.html" title="24.1. Locale Support">Section 24.1</a> for more information. If this variable is
set to the empty string (which is the default) then the value
is inherited from the execution environment of the server in a
system-dependent way.
</p></dd><dt id="GUC-LC-TIME"><span class="term"><code class="varname">lc_time</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.3.2.10.1.3" class="indexterm"></a>
</span></dt><dd><p>
Sets the locale to use for formatting dates and times, for example
with the <code class="function">to_char</code> family of
functions. Acceptable values are system-dependent; see <a class="xref" href="locale.html" title="24.1. Locale Support">Section 24.1</a> for more information. If this variable is
set to the empty string (which is the default) then the value
is inherited from the execution environment of the server in a
system-dependent way.
</p></dd><dt id="GUC-DEFAULT-TEXT-SEARCH-CONFIG"><span class="term"><code class="varname">default_text_search_config</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.3.2.11.1.3" class="indexterm"></a>
</span></dt><dd><p>
Selects the text search configuration that is used by those variants
of the text search functions that do not have an explicit argument
specifying the configuration.
See <a class="xref" href="textsearch.html" title="Chapter 12. Full Text Search">Chapter 12</a> for further information.
The built-in default is <code class="literal">pg_catalog.simple</code>, but
<span class="application">initdb</span> will initialize the
configuration file with a setting that corresponds to the
chosen <code class="varname">lc_ctype</code> locale, if a configuration
matching that locale can be identified.
</p></dd></dl></div></div><div class="sect2" id="RUNTIME-CONFIG-CLIENT-PRELOAD"><div class="titlepage"><div><div><h3 class="title">20.11.3. Shared Library Preloading</h3></div></div></div><p>
Several settings are available for preloading shared libraries into the
server, in order to load additional functionality or achieve performance
benefits. For example, a setting of
<code class="literal">'$libdir/mylib'</code> would cause
<code class="literal">mylib.so</code> (or on some platforms,
<code class="literal">mylib.sl</code>) to be preloaded from the installation's standard
library directory. The differences between the settings are when they
take effect and what privileges are required to change them.
</p><p>
<span class="productname">PostgreSQL</span> procedural language libraries can
be preloaded in this way, typically by using the
syntax <code class="literal">'$libdir/plXXX'</code> where
<code class="literal">XXX</code> is <code class="literal">pgsql</code>, <code class="literal">perl</code>,
<code class="literal">tcl</code>, or <code class="literal">python</code>.
</p><p>
Only shared libraries specifically intended to be used with PostgreSQL
can be loaded this way. Every PostgreSQL-supported library has
a <span class="quote">“<span class="quote">magic block</span>”</span> that is checked to guarantee compatibility. For
this reason, non-PostgreSQL libraries cannot be loaded in this way. You
might be able to use operating-system facilities such
as <code class="envar">LD_PRELOAD</code> for that.
</p><p>
In general, refer to the documentation of a specific module for the
recommended way to load that module.
</p><div class="variablelist"><dl class="variablelist"><dt id="GUC-LOCAL-PRELOAD-LIBRARIES"><span class="term"><code class="varname">local_preload_libraries</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.4.6.1.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.4.6.1.1.4" class="indexterm"></a>
</span></dt><dd><p>
This variable specifies one or more shared libraries that are to be
preloaded at connection start.
It contains a comma-separated list of library names, where each name
is interpreted as for the <a class="link" href="sql-load.html" title="LOAD"><code class="command">LOAD</code></a> command.
Whitespace between entries is ignored; surround a library name with
double quotes if you need to include whitespace or commas in the name.
The parameter value only takes effect at the start of the connection.
Subsequent changes have no effect. If a specified library is not
found, the connection attempt will fail.
</p><p>
This option can be set by any user. Because of that, the libraries
that can be loaded are restricted to those appearing in the
<code class="filename">plugins</code> subdirectory of the installation's
standard library directory. (It is the database administrator's
responsibility to ensure that only <span class="quote">“<span class="quote">safe</span>”</span> libraries
are installed there.) Entries in <code class="varname">local_preload_libraries</code>
can specify this directory explicitly, for example
<code class="literal">$libdir/plugins/mylib</code>, or just specify
the library name — <code class="literal">mylib</code> would have
the same effect as <code class="literal">$libdir/plugins/mylib</code>.
</p><p>
The intent of this feature is to allow unprivileged users to load
debugging or performance-measurement libraries into specific sessions
without requiring an explicit <code class="command">LOAD</code> command. To that end,
it would be typical to set this parameter using
the <code class="envar">PGOPTIONS</code> environment variable on the client or by
using
<code class="command">ALTER ROLE SET</code>.
</p><p>
However, unless a module is specifically designed to be used in this way by
non-superusers, this is usually not the right setting to use. Look
at <a class="xref" href="runtime-config-client.html#GUC-SESSION-PRELOAD-LIBRARIES">session_preload_libraries</a> instead.
</p></dd><dt id="GUC-SESSION-PRELOAD-LIBRARIES"><span class="term"><code class="varname">session_preload_libraries</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.4.6.2.1.3" class="indexterm"></a>
</span></dt><dd><p>
This variable specifies one or more shared libraries that are to be
preloaded at connection start.
It contains a comma-separated list of library names, where each name
is interpreted as for the <a class="link" href="sql-load.html" title="LOAD"><code class="command">LOAD</code></a> command.
Whitespace between entries is ignored; surround a library name with
double quotes if you need to include whitespace or commas in the name.
The parameter value only takes effect at the start of the connection.
Subsequent changes have no effect. If a specified library is not
found, the connection attempt will fail.
Only superusers and users with the appropriate <code class="literal">SET</code>
privilege can change this setting.
</p><p>
The intent of this feature is to allow debugging or
performance-measurement libraries to be loaded into specific sessions
without an explicit
<code class="command">LOAD</code> command being given. For
example, <a class="xref" href="auto-explain.html" title="F.4. auto_explain">auto_explain</a> could be enabled for all
sessions under a given user name by setting this parameter
with <code class="command">ALTER ROLE SET</code>. Also, this parameter can be changed
without restarting the server (but changes only take effect when a new
session is started), so it is easier to add new modules this way, even
if they should apply to all sessions.
</p><p>
Unlike <a class="xref" href="runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">shared_preload_libraries</a>, there is no large
performance advantage to loading a library at session start rather than
when it is first used. There is some advantage, however, when
connection pooling is used.
</p></dd><dt id="GUC-SHARED-PRELOAD-LIBRARIES"><span class="term"><code class="varname">shared_preload_libraries</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.4.6.3.1.3" class="indexterm"></a>
</span></dt><dd><p>
This variable specifies one or more shared libraries to be preloaded at
server start.
It contains a comma-separated list of library names, where each name
is interpreted as for the <a class="link" href="sql-load.html" title="LOAD"><code class="command">LOAD</code></a> command.
Whitespace between entries is ignored; surround a library name with
double quotes if you need to include whitespace or commas in the name.
This parameter can only be set at server start. If a specified
library is not found, the server will fail to start.
</p><p>
Some libraries need to perform certain operations that can only take
place at postmaster start, such as allocating shared memory, reserving
light-weight locks, or starting background workers. Those libraries
must be loaded at server start through this parameter. See the
documentation of each library for details.
</p><p>
Other libraries can also be preloaded. By preloading a shared library,
the library startup time is avoided when the library is first used.
However, the time to start each new server process might increase
slightly, even if that process never uses the library. So this
parameter is recommended only for libraries that will be used in most
sessions. Also, changing this parameter requires a server restart, so
this is not the right setting to use for short-term debugging tasks,
say. Use <a class="xref" href="runtime-config-client.html#GUC-SESSION-PRELOAD-LIBRARIES">session_preload_libraries</a> for that
instead.
</p><div class="note"><h3 class="title">Note</h3><p>
On Windows hosts, preloading a library at server start will not reduce
the time required to start each new server process; each server process
will re-load all preload libraries. However, <code class="varname">shared_preload_libraries
</code> is still useful on Windows hosts for libraries that need to
perform operations at postmaster start time.
</p></div></dd><dt id="GUC-JIT-PROVIDER"><span class="term"><code class="varname">jit_provider</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.4.6.4.1.3" class="indexterm"></a>
</span></dt><dd><p>
This variable is the name of the JIT provider library to be used
(see <a class="xref" href="jit-extensibility.html#JIT-PLUGGABLE" title="32.4.2. Pluggable JIT Providers">Section 32.4.2</a>).
The default is <code class="literal">llvmjit</code>.
This parameter can only be set at server start.
</p><p>
If set to a non-existent library, <acronym class="acronym">JIT</acronym> will not be
available, but no error will be raised. This allows JIT support to be
installed separately from the main
<span class="productname">PostgreSQL</span> package.
</p></dd></dl></div></div><div class="sect2" id="RUNTIME-CONFIG-CLIENT-OTHER"><div class="titlepage"><div><div><h3 class="title">20.11.4. Other Defaults</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt id="GUC-DYNAMIC-LIBRARY-PATH"><span class="term"><code class="varname">dynamic_library_path</code> (<code class="type">string</code>)
<a id="id-1.6.7.14.5.2.1.1.3" class="indexterm"></a>
<a id="id-1.6.7.14.5.2.1.1.4" class="indexterm"></a>
</span></dt><dd><p>
If a dynamically loadable module needs to be opened and the
file name specified in the <code class="command">CREATE FUNCTION</code> or
<code class="command">LOAD</code> command
does not have a directory component (i.e., the
name does not contain a slash), the system will search this
path for the required file.
</p><p>
The value for <code class="varname">dynamic_library_path</code> must be a
list of absolute directory paths separated by colons (or semi-colons
on Windows). If a list element starts
with the special string <code class="literal">$libdir</code>, the
compiled-in <span class="productname">PostgreSQL</span> package
library directory is substituted for <code class="literal">$libdir</code>; this
is where the modules provided by the standard
<span class="productname">PostgreSQL</span> distribution are installed.
(Use <code class="literal">pg_config --pkglibdir</code> to find out the name of
this directory.) For example:
</p><pre class="programlisting">
dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
</pre><p>
or, in a Windows environment:
</p><pre class="programlisting">
dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
</pre><p>
</p><p>
The default value for this parameter is
<code class="literal">'$libdir'</code>. If the value is set to an empty
string, the automatic path search is turned off.
</p><p>
This parameter can be changed at run time by superusers and users
with the appropriate <code class="literal">SET</code> privilege, but a
setting done that way will only persist until the end of the
client connection, so this method should be reserved for
development purposes. The recommended way to set this parameter
is in the <code class="filename">postgresql.conf</code> configuration
file.
</p></dd><dt id="GUC-GIN-FUZZY-SEARCH-LIMIT"><span class="term"><code class="varname">gin_fuzzy_search_limit</code> (<code class="type">integer</code>)
<a id="id-1.6.7.14.5.2.2.1.3" class="indexterm"></a>
</span></dt><dd><p>
Soft upper limit of the size of the set returned by GIN index scans. For more
information see <a class="xref" href="gin-tips.html" title="70.5. GIN Tips and Tricks">Section 70.5</a>.
</p></dd></dl></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="runtime-config-autovacuum.html" title="20.10. Automatic Vacuuming">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="runtime-config.html" title="Chapter 20. Server Configuration">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="runtime-config-locks.html" title="20.12. Lock Management">Next</a></td></tr><tr><td width="40%" align="left" valign="top">20.10. Automatic Vacuuming </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.6 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 20.12. Lock Management</td></tr></table></div></body></html>
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