Re: Why copy_relation_data only use wal whenWALarchivingis enabled - Mailing list pgsql-hackers

From Simon Riggs
Subject Re: Why copy_relation_data only use wal whenWALarchivingis enabled
Date
Msg-id 1192642189.4233.129.camel@ebony.site
Whole thread Raw
In response to Re: Why copy_relation_data only use wal whenWALarchivingis enabled  (Heikki Linnakangas <heikki@enterprisedb.com>)
Responses Re: Why copy_relation_data only use walwhenWALarchivingis enabled
List pgsql-hackers
On Wed, 2007-10-17 at 18:13 +0100, Heikki Linnakangas wrote:

> > The test script you
> > showed cheats six-ways-from-Sunday to cause an OID collision that would
> > never happen in practice.  The only case where it would really happen
> > is if a table that has existed for a long time (~ 2^32 OID creations)
> > gets dropped and then you're unlucky enough to recycle that exact OID
> > before the next checkpoint --- and then crash before the checkpoint.
> 
> Yeah, it's unlikely to happen, but the consequences are horrible.

When is this going to happen?

We'd need to insert 2^32 toast chunks, which is >4 TB of data, or insert
2^32 large objects, or create 2^32 tables, or any combination of the
above all within one checkpoint duration *and* exactly hit the exact
same relation.

That's a weird and huge application, a very fast server and an unlucky
DBA to hit the exact OID to be reused and then have the server crash so
we'll ever notice.

--  Simon Riggs 2ndQuadrant  http://www.2ndQuadrant.com



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