Re: Automatic cleanup of oldest WAL segments with pg_receivexlog

On Fri, Feb 24, 2017 at 11:56 AM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:
> On 2/23/17 8:47 PM, Michael Paquier wrote:
>>
>> Anything else than measured in bytes either requires a lookup at the
>> file timestamp, which is not reliable with noatime or a lookup at WAL
>> itself to decide when is the commit timestamp that matches the oldest
>> point in time of the backup policy.
>
> An indication that it'd be nice to have a better way to store this
> information as part of a base backup, or the archived WAL files.

An idea here would be to add in the long header of the segment a
timestamp of when it was created. This is inherent to only the server
generating the WAL.

>> That could be made performance
>> wise with an archive command. With pg_receivexlog you could make use
>> of the end-segment command to scan the completely written segment for
>> this data before moving on to the next one. At least it gives an
>> argument for having such a command. David Steele mentioned that he
>> could make use of such a thing.
>
> BTW, I'm not opposed to an end-segment command; I'm just saying I don't
> think having it would really help users very much.

Thanks. Yes that's hard to come up here with something that would
satisfy enough users without giving much maintenance penalty.
--
Michael