Re: BUG #7890: wrong behaviour using pg_rotate_logfile() with parameter log_truncate_on_rotation = on

On Monday, February 18, 2013 8:28 PM Rafael Martinez wrote:
> On 02/18/2013 03:41 PM, Amit Kapila wrote:
> [...........]
> > Why you think this is wrong behavior, do you expect any time you
> > call pg_rotate_logfile(), it should truncate the file if
> > log_truncate_on_rotation is on? I think if you are expecting such
> > behavior, it might not be right expectation, because it considers
> > the the time and log_filename format as well.
> >
>=20
> Hello
>=20
> I agree with Sari in this report.
>=20
> If you call pg_rotate_logfile() AND log_truncate_on_rotation is on,
> the logfile should be truncated. This should happen even if the
> logfile name does not change during rotation, and even if
> log_rotation_age / log_rotation_size are defined.
>=20
> According to the documentation:
>=20
> "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 ..."

Further description for log_truncate_on_rotation is as follows:

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.

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.=20

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.

In the examples, it is clearly shown that, truncation will not happen =
only on based of log_truncate_on_rotation.


> "... pg_rotate_logfile signals the log-file manager to switch to a new
> output file immediately"

By reading the description of pg_rotate_logfile, it can mean that this =
is function to achieve what you are saying.
But as per code, it is not so.

By the way, why you want this function to behave in such a way, that it =
can override the meaning of other log parameters?

With Regards,
Amit Kapila.