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Re: WAL logs and segment files

From: "scott" <scott(at)QNET(dot)COM>
To: "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: <eeeggg499(at)netscape(dot)net>, "Cc:" <pgsql-admin(at)postgresql(dot)org>
Subject: Re: WAL logs and segment files
Date: 2004-02-21 00:10:59
Message-ID: 001b01c3f80f$2fcd7de0$9edfddd1@scott (view raw or flat)
Thread:
Lists: pgsql-admin
Take me off your list! You have the wrong scott!
----- Original Message ----- 
From: "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: "Eduardo Leva" <eeeggg499(at)netscape(dot)net>
Cc: <pgsql-admin(at)postgresql(dot)org>
Sent: Friday, February 20, 2004 12:29 PM
Subject: Re: [ADMIN] WAL logs and segment files


> Eduardo Leva wrote:
> > Hi, guys... I'm reading the version 7.3.4 documentation and I found
this: "
> >
> > "WAL logs are stored in the directory $PGDATA/pg_xlog, as a set of
segment
> >  files, each 16 MB in size. Each segment is divided into 8 kB pages. The
> >  log record headers are described in access/xlog.h; record content is
> >  dependent on the type of event that is being logged. Segment files are
> >  given ever-increasing numbers as names, starting at 0000000000000000.
The
> >  numbers do not wrap, at present, but it should take a very long time to
> >  exhaust the available stock of numbers. "
> >
> > in item 12.2 Implementation. The question is: How do I solve this
> > situation, the remarked situation? The answer is not in the docs.
Thanks.
>
> What situation do you need to solve?  The wrapping?  The documention
> states "a very long time", but it more of a joke.  That number would be
> huge to wrap around and you would be updating your PostgreSQL version
> long before it would ever wrap.
>
> The number is actually an int8 that has a maximum value of:
>
> 18446744073709551616
>
> -- 
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
>   +  If your life is a hard drive,     |  13 Roberts Road
>   +  Christ can be your backup.        |  Newtown Square, Pennsylvania
19073
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match


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