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Re: WAL logs and segment files

From: kaolin fire <cognosco(at)tentacle(dot)net>
To: pgsql-admin(at)postgresql(dot)org
Subject: Re: WAL logs and segment files
Date: 2004-02-20 22:05:49
Message-ID: F13EF376-63F0-11D8-9105-000A957FF036@tentacle.net (view raw or flat)
Thread:
Lists: pgsql-admin
If you know where I can get a 1.5e+11 terabyte drive, I'd love to hear 
it. ;)

-kaolin fire
-http://erif.org/code/fallingup/

On Feb 20, 2004, at 12:29 PM, Bruce Momjian wrote:

> 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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