Re: Idea: recycle WAL segments, don't delete/recreate 'em - Mailing list pgsql-hackers

From Patrick Macdonald
Subject Re: Idea: recycle WAL segments, don't delete/recreate 'em
Date
Msg-id 3B559CAB.58DB931A@redhat.com
Whole thread Raw
In response to Idea: recycle WAL segments, don't delete/recreate 'em  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Idea: recycle WAL segments, don't delete/recreate 'em  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: Idea: recycle WAL segments, don't delete/recreate 'em  (Bruce Momjian <pgman@candle.pha.pa.us>)
List pgsql-hackers
Hmmm... my prior appends to this newsgroup are stalled.  Hopefully,
they'll be available soon.

Tom Lane wrote:
> 
> What you may really be saying is that the existing scheme for management
> of log segments is inappropriate for PIT usage; if so feel free to
> propose a better one.  But I don't see how recycling of no-longer-wanted
> segments can break anything.

Yes, but in a very roundabout way (or so it seems).  The main point
that I was trying to illustrate was that if a database supports 
point-in-time recovery, recycling of the only available log segments 
is a bad thing.  And, yes, in practice if you have point-in-time
recovery enabled you better archive your logs with your backup to
ensure that you can roll forward as expected.

A possible solution (as I mentioned before)) is to have 2 methods
of logging available: circular and forward-recoverable.  When a
database is created, the creator selects which type of logging to
perform.  The log segments are exactly the same, only the recycling
method is different.

Hmmm... the more I look at this, the more interested I become.

Cheers,
Patrick


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