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<title>17.7.Error Reporting and Logging</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="runtime-config-logging"></a>17.7.Error Reporting and Logging</h2></div></div></div>
<a name="id650358"></a><div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="runtime-config-logging-where"></a>17.7.1.Where To Log</h3></div></div></div>
<a name="id650379"></a><div class="variablelist"><dl>
<dt>
<a name="guc-log-destination"></a><span class="term"><code class="varname">log_destination</code> (<code class="type">string</code>)</span>
</dt>
<dd><p> <span class="productname">PostgreSQL</span> supports several methods
for logging server messages, including
<span class="systemitem">stderr</span> and
<span class="systemitem">syslog</span>. On Windows,
<span class="systemitem">eventlog</span> is also supported. Set this
option to a list of desired log destinations separated by
commas. The default is to log to <span class="systemitem">stderr</span>
only.
This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p></dd>
<dt>
<a name="guc-redirect-stderr"></a><span class="term"><code class="varname">redirect_stderr</code> (<code class="type">boolean</code>)</span>
</dt>
<dd><p> This option allows messages sent to <span class="application">stderr</span> to be
captured and redirected into log files.
This option, in combination with logging to <span class="application">stderr</span>,
is often more useful than
logging to <span class="application">syslog</span>, since some types of messages
may not appear in <span class="application">syslog</span> output (a common example
is dynamic-linker failure messages).
This option can only be set at server start.
</p></dd>
<dt>
<a name="guc-log-directory"></a><span class="term"><code class="varname">log_directory</code> (<code class="type">string</code>)</span>
</dt>
<dd><p> When <code class="varname">redirect_stderr</code> is enabled, this option
determines the directory in which log files will be created.
It may be specified as an absolute path, or relative to the
cluster data directory.
This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p></dd>
<dt>
<a name="guc-log-filename"></a><span class="term"><code class="varname">log_filename</code> (<code class="type">string</code>)</span>
</dt>
<dd><p> When <code class="varname">redirect_stderr</code> is enabled, this option
sets the file names of the created log files. The value
is treated as a <span class="systemitem">strftime</span> pattern,
so <code class="literal">%</code>-escapes
can be used to specify time-varying file names.
If no <code class="literal">%</code>-escapes are present,
<span class="productname">PostgreSQL</span> will
append the epoch of the new log file's open time. For example,
if <code class="varname">log_filename</code> were <code class="literal">server_log</code>, then the
chosen file name would be <code class="literal">server_log.1093827753</code>
for a log starting at Sun Aug 29 19:02:33 2004 MST.
This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p></dd>
<dt>
<a name="guc-log-rotation-age"></a><span class="term"><code class="varname">log_rotation_age</code> (<code class="type">integer</code>)</span>
</dt>
<dd><p> When <code class="varname">redirect_stderr</code> is enabled, this option
determines the maximum lifetime of an individual log file.
After this many minutes have elapsed, a new log file will
be created. Set to zero to disable time-based creation of
new log files.
This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p></dd>
<dt>
<a name="guc-log-rotation-size"></a><span class="term"><code class="varname">log_rotation_size</code> (<code class="type">integer</code>)</span>
</dt>
<dd><p> When <code class="varname">redirect_stderr</code> is enabled, this option
determines the maximum size of an individual log file.
After this many kilobytes have been emitted into a log file,
a new log file will be created. Set to zero to disable size-based
creation of new log files.
This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p></dd>
<dt>
<a name="guc-log-truncate-on-rotation"></a><span class="term"><code class="varname">log_truncate_on_rotation</code> (<code class="type">boolean</code>)</span>
</dt>
<dd>
<p> When <code class="varname">redirect_stderr</code> is enabled, this option will cause
<span class="productname">PostgreSQL</span> to truncate (overwrite),
rather than append to, any existing log file of the same name.
However, truncation will occur only when a new file is being opened
due to time-based rotation, not during server startup or size-based
rotation. When off, pre-existing files will be appended to in
all cases. For example, using this option in combination with
a <code class="varname">log_filename</code> like <code class="literal">postgresql-%H.log</code>
would result in generating twenty-four hourly log files and then
cyclically overwriting them.
This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p>
<p> Example: To keep 7 days of logs, one log file per day named
<code class="literal">server_log.Mon</code>, <code class="literal">server_log.Tue</code>,
etc, and automatically overwrite last week's log with this week's log,
set <code class="varname">log_filename</code> to <code class="literal">server_log.%a</code>,
<code class="varname">log_truncate_on_rotation</code> to <code class="literal">on</code>, and
<code class="varname">log_rotation_age</code> to <code class="literal">1440</code>.
</p>
<p> Example: To keep 24 hours of logs, one log file per hour, but
also rotate sooner if the log file size exceeds 1GB, set
<code class="varname">log_filename</code> to <code class="literal">server_log.%H%M</code>,
<code class="varname">log_truncate_on_rotation</code> to <code class="literal">on</code>,
<code class="varname">log_rotation_age</code> to <code class="literal">60</code>, and
<code class="varname">log_rotation_size</code> to <code class="literal">1000000</code>.
Including <code class="literal">%M</code> in <code class="varname">log_filename</code> allows
any size-driven rotations that may occur to select a file name
different from the hour's initial file name.
</p>
</dd>
<dt>
<a name="guc-syslog-facility"></a><span class="term"><code class="varname">syslog_facility</code> (<code class="type">string</code>)</span>
</dt>
<dd><p> When logging to <span class="application">syslog</span> is enabled, this option
determines the <span class="application">syslog</span>
“<span class="quote">facility</span>” to be used. You may choose
from <code class="literal">LOCAL0</code>, <code class="literal">LOCAL1</code>,
<code class="literal">LOCAL2</code>, <code class="literal">LOCAL3</code>, <code class="literal">LOCAL4</code>,
<code class="literal">LOCAL5</code>, <code class="literal">LOCAL6</code>, <code class="literal">LOCAL7</code>;
the default is <code class="literal">LOCAL0</code>. See also the
documentation of your system's
<span class="application">syslog</span> daemon.
This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p></dd>
<dt>
<a name="guc-syslog-ident"></a><span class="term"><code class="varname">syslog_ident</code> (<code class="type">string</code>)</span>
</dt>
<dd><p> When logging to <span class="application">syslog</span> is enabled, this option
determines the program name used to identify
<span class="productname">PostgreSQL</span> messages in
<span class="application">syslog</span> logs. The default is
<code class="literal">postgres</code>.
This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p></dd>
</dl></div>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="runtime-config-logging-when"></a>17.7.2.When To Log</h3></div></div></div>
<div class="variablelist"><dl>
<dt>
<a name="guc-client-min-messages"></a><span class="term"><code class="varname">client_min_messages</code> (<code class="type">string</code>)</span>
</dt>
<dd><p> Controls which message levels 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>, <code class="literal">ERROR</code>, <code class="literal">FATAL</code>,
and <code class="literal">PANIC</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 <code class="varname">log_min_messages</code>.
</p></dd>
<dt>
<a name="guc-log-min-messages"></a><span class="term"><code class="varname">log_min_messages</code> (<code class="type">string</code>)</span>
</dt>
<dd><p> Controls which message levels are written to the server log.
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">INFO</code>, <code class="literal">NOTICE</code>, <code class="literal">WARNING</code>,
<code class="literal">ERROR</code>, <code class="literal">LOG</code>, <code class="literal">FATAL</code>, and
<code class="literal">PANIC</code>. Each level includes all the levels that
follow it. The later the level, the fewer messages are sent
to the log. The default is <code class="literal">NOTICE</code>. Note that
<code class="literal">LOG</code> has a different rank here than in
<code class="varname">client_min_messages</code>.
Only superusers can change this setting.
</p></dd>
<dt>
<a name="guc-log-error-verbosity"></a><span class="term"><code class="varname">log_error_verbosity</code> (<code class="type">string</code>)</span>
</dt>
<dd><p> Controls the amount of detail written in the server log for each
message that is logged. Valid values are <code class="literal">TERSE</code>,
<code class="literal">DEFAULT</code>, and <code class="literal">VERBOSE</code>, each adding more
fields to displayed messages.
Only superusers can change this setting.
</p></dd>
<dt>
<a name="guc-log-min-error-statement"></a><span class="term"><code class="varname">log_min_error_statement</code> (<code class="type">string</code>)</span>
</dt>
<dd><p> Controls whether or not the SQL statement that causes an error
condition will also be recorded in the server log. All SQL
statements that cause an error of the specified level or
higher are logged. The default is
<code class="literal">PANIC</code> (effectively turning this feature
off for normal use). 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">INFO</code>, <code class="literal">NOTICE</code>,
<code class="literal">WARNING</code>, <code class="literal">ERROR</code>,
<code class="literal">FATAL</code>, and <code class="literal">PANIC</code>. For
example, if you set this to <code class="literal">ERROR</code> then all
SQL statements causing errors, fatal errors, or panics will be
logged. Enabling this option can be helpful in tracking down
the source of any errors that appear in the server log.
Only superusers can change this setting.
</p></dd>
<dt>
<a name="guc-log-min-duration-statement"></a><span class="term"><code class="varname">log_min_duration_statement</code> (<code class="type">integer</code>)</span>
</dt>
<dd><p> Logs the statement and its duration on a single log line if its
duration is greater than or equal to the specified number of
milliseconds. Setting this to zero will print all statements
and their durations. Minus-one (the default) disables the
feature. For example, if you set it to <code class="literal">250</code>
then all SQL statements that run 250ms or longer will be
logged. Enabling this option can be useful in tracking down
unoptimized queries in your applications. This setting is
independent of <code class="varname">log_statement</code> and
<code class="varname">log_duration</code>. Only superusers can change
this setting.
</p></dd>
<dt>
<a name="guc-silent-mode"></a><span class="term"><code class="varname">silent_mode</code> (<code class="type">boolean</code>)</span>
</dt>
<dd><p> Runs the server silently. If this option is set, the server
will automatically run in background and any controlling
terminals are disassociated (same effect as
<code class="command">postmaster</code>'s <code class="option">-S</code> option).
The server's standard output and standard error are redirected
to <code class="literal">/dev/null</code>, so any messages sent to them will be lost.
Unless <span class="application">syslog</span> logging is selected or
<code class="varname">redirect_stderr</code> is enabled, using this option
is discouraged because it makes it impossible to see error messages.
</p></dd>
</dl></div>
<p> Here is a list of the various message severity levels used in
these settings:
</p>
<div class="variablelist"><dl>
<dt><span class="term"><code class="literal">DEBUG[1-5]</code></span></dt>
<dd><p> Provides information for use by developers.
</p></dd>
<dt><span class="term"><code class="literal">INFO</code></span></dt>
<dd><p> Provides information implicitly requested by the user,
e.g., during <code class="command">VACUUM VERBOSE</code>.
</p></dd>
<dt><span class="term"><code class="literal">NOTICE</code></span></dt>
<dd><p> Provides information that may be helpful to users, e.g.,
truncation of long identifiers and the creation of indexes as part
of primary keys.
</p></dd>
<dt><span class="term"><code class="literal">WARNING</code></span></dt>
<dd><p> Provides warnings to the user, e.g., <code class="command">COMMIT</code>
outside a transaction block.
</p></dd>
<dt><span class="term"><code class="literal">ERROR</code></span></dt>
<dd><p> Reports an error that caused the current command to abort.
</p></dd>
<dt><span class="term"><code class="literal">LOG</code></span></dt>
<dd><p> Reports information of interest to administrators, e.g.,
checkpoint activity.
</p></dd>
<dt><span class="term"><code class="literal">FATAL</code></span></dt>
<dd><p> Reports an error that caused the current session to abort.
</p></dd>
<dt><span class="term"><code class="literal">PANIC</code></span></dt>
<dd><p> Reports an error that caused all sessions to abort.
</p></dd>
</dl></div>
<p>
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="runtime-config-logging-what"></a>17.7.3.What To Log</h3></div></div></div>
<div class="variablelist"><dl>
<dt>
<span xmlns="http://www.w3.org/TR/xhtml1/transitional" class="term"><code xmlns="" class="varname">debug_print_parse</code> (<code xmlns="" class="type">boolean</code>)</span><br xmlns="http://www.w3.org/TR/xhtml1/transitional"></br><span xmlns="http://www.w3.org/TR/xhtml1/transitional" class="term"><code xmlns="" class="varname">debug_print_rewritten</code> (<code xmlns="" class="type">boolean</code>)</span><br xmlns="http://www.w3.org/TR/xhtml1/transitional"></br><span xmlns="http://www.w3.org/TR/xhtml1/transitional" class="term"><code xmlns="" class="varname">debug_print_plan</code> (<code xmlns="" class="type">boolean</code>)</span><br xmlns="http://www.w3.org/TR/xhtml1/transitional"></br><span class="term"><code class="varname">debug_pretty_print</code> (<code class="type">boolean</code>)</span>
</dt>
<dd><p> These options enable various debugging output to be emitted.
For each executed query, they print
the resulting parse tree, the query rewriter output, or the
execution plan. <code class="varname">debug_pretty_print</code> indents
these displays to produce a more readable but much longer
output format. <code class="varname">client_min_messages</code> or
<code class="varname">log_min_messages</code> must be
<code class="literal">DEBUG1</code> or lower to actually send this output
to the client or the server log, respectively.
These options are off by default.
</p></dd>
<dt>
<a name="guc-log-connections"></a><span class="term"><code class="varname">log_connections</code> (<code class="type">boolean</code>)</span>
</dt>
<dd><p> This outputs a line to the server log detailing each successful
connection. This is off by default, although it is probably very
useful. Some client programs, like <span class="application">psql</span>, attempt
to connect twice while determining if a password is required, so
duplicate “<span class="quote">connection received</span>” messages do not
necessarily indicate a problem. This option can only be set at
server start or in the <code class="filename">postgresql.conf</code> configuration file.
</p></dd>
<dt>
<a name="guc-log-disconnections"></a><span class="term"><code class="varname">log_disconnections</code> (<code class="type">boolean</code>)</span>
</dt>
<dd><p> This outputs a line in the server log similar to
<code class="varname">log_connections</code> but at session termination,
and includes the duration of the session. This is off by
default. This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p></dd>
<dt>
<a name="guc-log-duration"></a><span class="term"><code class="varname">log_duration</code> (<code class="type">boolean</code>)</span>
</dt>
<dd><p> Causes the duration of every completed statement which satisfies
<code class="varname">log_statement</code> to be logged. When using this option,
if you are not using <span class="application">syslog</span>, it is recommended
that you log the PID or session ID using <code class="varname">log_line_prefix</code>
so that you can link the statement message to the later
duration message using the process ID or session ID. The default is
<code class="literal">off</code>. Only superusers can change this setting.
</p></dd>
<dt>
<a name="guc-log-line-prefix"></a><span class="term"><code class="varname">log_line_prefix</code> (<code class="type">string</code>)</span>
</dt>
<dd>
<p> This is a <code class="function">printf</code>-style string that is output at the
beginning of each log line. The default is an empty string.
Each recognized escape is replaced as outlined
below - anything else that looks like an escape is ignored. Other
characters are copied straight to the log line. Some escapes are
only recognized by session processes, and do not apply to
background processes such as the postmaster. <span class="application">Syslog</span>
produces its own
time stamp and process ID information, so you probably do not want to
use those escapes if you are using <span class="application">syslog</span>.
This option can be set at server start or in the
<code class="filename">postgresql.conf</code> configuration file.
</p>
<div class="informaltable"><table border="1">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Escape</th>
<th>Effect</th>
<th>Session only</th>
</tr></thead>
<tbody>
<tr>
<td><code class="literal">%u</code></td>
<td>User name</td>
<td>yes</td>
</tr>
<tr>
<td><code class="literal">%d</code></td>
<td>Database name</td>
<td>yes</td>
</tr>
<tr>
<td><code class="literal">%r</code></td>
<td>Remote host name or IP address, and remote port</td>
<td>yes</td>
</tr>
<tr>
<td><code class="literal">%h</code></td>
<td>Remote host name or IP address</td>
<td>yes</td>
</tr>
<tr>
<td><code class="literal">%p</code></td>
<td>Process ID</td>
<td>no</td>
</tr>
<tr>
<td><code class="literal">%t</code></td>
<td>Time stamp (no milliseconds)</td>
<td>no</td>
</tr>
<tr>
<td><code class="literal">%m</code></td>
<td>Time stamp with milliseconds</td>
<td>no</td>
</tr>
<tr>
<td><code class="literal">%i</code></td>
<td>Command tag: This is the command that generated the log line.</td>
<td>yes</td>
</tr>
<tr>
<td><code class="literal">%c</code></td>
<td>Session ID: A unique identifier for each session.
It is 2 4-byte hexadecimal numbers (without leading zeros)
separated by a dot. The numbers
are the session start time and the process ID, so this can also
be used as a space saving way of printing these items.</td>
<td>yes</td>
</tr>
<tr>
<td><code class="literal">%l</code></td>
<td>Number of the log line for each process, starting at 1</td>
<td>no</td>
</tr>
<tr>
<td><code class="literal">%s</code></td>
<td>Session start time stamp</td>
<td>yes</td>
</tr>
<tr>
<td><code class="literal">%x</code></td>
<td>Transaction ID</td>
<td>yes</td>
</tr>
<tr>
<td><code class="literal">%q</code></td>
<td>Does not produce any output, but tells non-session
processes to stop at this point in the string. Ignored by
session processes.</td>
<td>no</td>
</tr>
<tr>
<td><code class="literal">%%</code></td>
<td>Literal <code class="literal">%</code>
</td>
<td>no</td>
</tr>
</tbody>
</table></div>
<p>
</p>
</dd>
<dt>
<a name="guc-log-statement"></a><span class="term"><code class="varname">log_statement</code> (<code class="type">string</code>)</span>
</dt>
<dd>
<p> Controls which SQL statements are logged. Valid values are
<code class="literal">none</code>, <code class="literal">ddl</code>, <code class="literal">mod</code>, and
<code class="literal">all</code>. <code class="literal">ddl</code> logs all data definition
commands like <code class="literal">CREATE</code>, <code class="literal">ALTER</code>, and
<code class="literal">DROP</code> commands. <code class="literal">mod</code> logs all
<code class="literal">ddl</code> statements, plus <code class="literal">INSERT</code>,
<code class="literal">UPDATE</code>, <code class="literal">DELETE</code>, <code class="literal">TRUNCATE</code>,
and <code class="literal">COPY FROM</code>. <code class="literal">PREPARE</code> and
<code class="literal">EXPLAIN ANALYZE</code> statements are also logged if their
contained command is of an appropriate type.
</p>
<p> The default is <code class="literal">none</code>. Only superusers can change this
setting.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p> The <code class="command">EXECUTE</code> statement is not considered a
<code class="literal">ddl</code> or <code class="literal">mod</code> statement. Statements that
generate syntax errors are not logged. Set
<code class="varname">log_min_error_statement</code> to <code class="literal">error</code> to
log such statements.
</p>
<p> When a function is defined in the
<span class="application">PL/pgSQL</span>server-side language, any queries
executed by the function will only be logged the first time that the
function is invoked in a particular session. This is because
<span class="application">PL/pgSQL</span> keeps a cache of the
query plans produced for the SQL statements in the function.
</p>
</div>
</dd>
<dt>
<a name="guc-log-hostname"></a><span class="term"><code class="varname">log_hostname</code> (<code class="type">boolean</code>)</span>
</dt>
<dd><p> By default, connection log messages only show the IP address of the
connecting host. Turning on this option causes logging of the
host name as well. Note that depending on your host name resolution
setup this might impose a non-negligible performance penalty. This
option can be set at server start or in the
<code class="filename">postgresql.conf</code> file.
</p></dd>
</dl></div>
</div>
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