{"Entry":{"collection":"guc","key":"log_truncate_on_rotation","name":"log_truncate_on_rotation","aliases":[],"metadata":{"baseline":false,"boot_human":"Not specified","boot_val":null,"category":"Reporting and Logging / Where to Log","category_zh":"","changed_in":[],"changes":[{"documentation_changed":false,"fields":{},"from":"7.4","status":"added","to":"8.0"},{"documentation_changed":true,"fields":{},"from":"8.0","status":"changed","to":"8.1"},{"documentation_changed":true,"fields":{},"from":"8.1","status":"changed","to":"8.2"},{"documentation_changed":true,"fields":{},"from":"8.2","status":"changed","to":"8.3"},{"documentation_changed":true,"fields":{},"from":"14","status":"changed","to":"15"}],"content_hash":"94e92f6da40d30489f7ab83dbcfd234433323b46a022c0cbeefb486ecce5180a","context":"","default_changed_in":[],"default_history":[{"from":"9.0","to":"19","value":"off"}],"editorial":{"advice":{"olap":"For analytical logs, confirm that long-running ingestion has finished before a repeating name is truncated; use unique names when completion cannot be guaranteed.","oltp":"Enable log_truncate_on_rotation only when time-based rotation intentionally reuses a filename and the previous file has been durably shipped or is meant to be replaced. Leave it off for unique timestamped names.","small":"A short repeating cycle can bound disk use, but truncation is not retention management. Monitor shipping and backups so the next time rotation cannot erase the only copy."},"mechanism":["log_truncate_on_rotation truncates existing log files of same name during log rotation. Truncation occurs when time-based rotation reuses an existing filename; size rotation and other causes do not apply the same overwrite rule.","log_truncate_on_rotation is a SIGHUP-context setting: a configuration reload activates the new server value without a restart; subsequent operations that consult it use the refreshed value.","The active path is composed from log_destination, logging_collector or syslog/eventlog, file naming and permissions, rotation triggers, and external shipping or retention."],"pitfalls":["Editing log_truncate_on_rotation without reloading configuration and verifying the effective value and subsequent behavior.","Combining incompatible destination, collector, filename, and rotation assumptions and then losing or overwriting logs.","Failing to monitor a full or unwritable log target, which can block logging or database activity depending on the path.","Expecting truncation on every rotation path; it is tied to time-based reuse of an existing filename."],"references":[{"title":"PostgreSQL 19 Beta 4: log_truncate_on_rotation","url":"https://www.postgresql.org/docs/19/runtime-config-logging.html#GUC-LOG-TRUNCATE-ON-ROTATION"},{"title":"PostgreSQL 19 release notes","url":"https://www.postgresql.org/docs/19/release-19.html"}],"related":["logging_collector","log_destination","log_directory","log_filename","log_rotation_age","log_rotation_size"],"summary":"log_truncate_on_rotation is the PostgreSQL setting that controls whether PostgreSQL truncates existing log files of same name during log rotation."},"enumvals":[],"first_version":"8.0","group":"Reporting and Logging","group_slug":"logging","imported_at":"2026-09-30T00:40:57.453548+08:00","intro_commit":{},"key":"log_truncate_on_rotation","last_version":"20","max_val":"","min_val":"","name":"log_truncate_on_rotation","position":256,"present_in":["8.0","8.1","8.2","8.3","8.4","9.0","9.1","9.2","9.3","9.4","9.5","9.6","10","11","12","13","14","15","16","17","18","19","20"],"short_desc":"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.","short_desc_zh":"","source_rev":"english-manuals:1f3eb48cf140ce5a9d9d91850e83a2bf6037b23e3a15cf249178e97f1a9871ad","unit":"","vartype":"bool"}},"Definition":{"Collection":"guc","Key":"log_truncate_on_rotation","SourceDatabase":"center","Version":"18","SourceTable":"guc","SourceKey":"log_truncate_on_rotation","SourceRevision":"english-manuals:1f3eb48cf140ce5a9d9d91850e83a2bf6037b23e3a15cf249178e97f1a9871ad","Facts":{"boot_val":"off","category":"Reporting and Logging / Where to Log","context":"sighup","description":"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.","doc":{"anchor":"GUC-LOG-TRUNCATE-ON-ROTATION","file":"runtime-config-logging.html","lang":"en","sha256":"93c48c522a72fca19705c4c91a71e951eae653662008eee2e4a9a74a11127fde","slug":"18"},"documented":true,"enumvals":null,"extra_desc":null,"lang":"en","max_val":null,"metadata_version":"18","min_val":null,"name":"log_truncate_on_rotation","short_desc":"Truncate existing log files of same name during log rotation.","source":"pg-settings-source-snapshot","unit":null,"vartype":"bool"},"ManualEvidence":{"doc":{"anchor":"GUC-LOG-TRUNCATE-ON-ROTATION","file":"runtime-config-logging.html","lang":"en","sha256":"93c48c522a72fca19705c4c91a71e951eae653662008eee2e4a9a74a11127fde","slug":"18"}},"MeasuredEvidence":{"metadata_version":"18"}},"Text":{"Collection":"guc","Key":"log_truncate_on_rotation","SourceDatabase":"center","Version":"18","Locale":"en","Title":"log_truncate_on_rotation","Summary":"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.","BodyHTML":"\u003cp\u003eWhen 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\u0026#39;s log with this week\u0026#39;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\u0026#39;s initial file name.\u003c/p\u003e","SourceRevision":"english-manuals:1f3eb48cf140ce5a9d9d91850e83a2bf6037b23e3a15cf249178e97f1a9871ad","ContentHash":"0ea9e5b034712a53506433c320fec1e1d3d16ba0c71a2d97922e388976dbec17","Payload":{"description":"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."}},"RequestedLocale":"zh-Hans","Fallback":true,"Versions":["10","11","12","13","14","15","16","17","18","19","20","8.0","8.1","8.2","8.3","8.4","9.0","9.1","9.2","9.3","9.4","9.5","9.6"],"Locales":["en"],"Signatures":null,"Spellings":null,"SQLState":null,"Evidence":null}