log_truncate_on_rotation

When logging_collector is enabled, this parameter will cause PostgreSQL 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 setting in combination with a log_filename like postgresql-%H.log would result in generating twenty-four hourly log files and then cyclically overwriting them. This parameter can only be set in the postgresql.conf file or on the server command line. Example: To keep 7 days of logs, one log file per day named server_log.Mon, server_log.Tue, etc., and automatically overwrite last week's log with this week's log, set log_filename to server_log.%a, log_truncate_on_rotation to on, and log_rotation_age to 1440. Example: To keep 24 hours of logs, one log file per hour, but also rotate sooner if the log file size exceeds 1GB, set log_filename to server_log.%H%M, log_truncate_on_rotation to on, log_rotation_age to 60, and log_rotation_size to 1000000. Including %M in log_filename allows any size-driven rotations that might occur to select a file name different from the hour's initial file name.

English manual coverage begins with PostgreSQL 7.4. Source history and runtime observations have their own recorded version boundaries.

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boot val: off
category: Reporting and Logging / Where to Log
context: sighup
doc same as: Unknown
documented: true
enumvals: Unknown
extra desc: Unknown
lang: en
max val: Unknown
metadata version: 18
min val: Unknown
name: log_truncate_on_rotation
short desc: Truncate existing log files of same name during log rotation.
source: pg-settings-source-snapshot
unit: Unknown
vartype: bool

Definition PG 18

When logging_collector is enabled, this parameter will cause PostgreSQL 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 setting in combination with a log_filename like postgresql-%H.log would result in generating twenty-four hourly log files and then cyclically overwriting them. This parameter can only be set in the postgresql.conf file or on the server command line.

Example: To keep 7 days of logs, one log file per day named server_log.Mon, server_log.Tue, etc., and automatically overwrite last week's log with this week's log, set log_filename to server_log.%a, log_truncate_on_rotation to on, and log_rotation_age to 1440.

Example: To keep 24 hours of logs, one log file per hour, but also rotate sooner if the log file size exceeds 1GB, set log_filename to server_log.%H%M, log_truncate_on_rotation to on, log_rotation_age to 60, and log_rotation_size to 1000000. Including %M in log_filename allows any size-driven rotations that might occur to select a file name different from the hour's initial file name.

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Complete source facts

doc html

<p>
        When <code class="varname">logging_collector</code> is enabled,
        this parameter 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 setting 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 parameter can only be set in the <code class="filename">postgresql.conf</code>
        file or on the server command line.
       </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 might occur to select a file name
        different from the hour's initial file name.
       </p>

documentation revision

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Source references

Original manual reference

Full definition and evidence JSON

Definition sources

center · PostgreSQL 18 · wiki-repair-20261023:ba2ed9297627c0b3b3d638cc60d015596b3a7ada38de45dbab54b7169423cf33

Text language: en · wiki-repair-20261023:ba2ed9297627c0b3b3d638cc60d015596b3a7ada38de45dbab54b7169423cf33