Thread

1. Re: WAL replay logic (was Re: [PERFORM] Mount options f

   Mikheev, Vadim <vmikheev@sectordata.com> — 2003-02-18T19:15:25Z

   > > > Added to TODO:
   > > >
   > > > 	* Allow WAL information to recover corrupted pg_controldata
   > > >...
   > > > >      Using pg_control to get the checkpoint position 
   > speeds up the
   > > > >      recovery process, but to handle possible 
   > corruption of pg_control,
   > > > >      we should actually implement the reading of 
   > existing log segments
   > > > >      in reverse order -- newest to oldest -- in order 
   > to find the last
   > > > >      checkpoint. This has not been implemented, yet.
   > > 
   > > So if you do this, do you still need to store that information in
   > > pg_control at all?
   
   Yes: to "speeds up the recovery process".
   
   Vadim
   
   
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2. Re: WAL replay logic (was Re: [PERFORM] Mount options f

   Curt Sampson <cjs@cynic.net> — 2003-02-19T02:53:22Z

   On Tue, 18 Feb 2003, Mikheev, Vadim wrote:
   
   > > > So if you do this, do you still need to store that information in
   > > > pg_control at all?
   >
   > Yes: to "speeds up the recovery process".
   
   If it's going to slow down the performance of my database when not doing
   recovery (because I have to write two files for every transaction,
   rather than one), I couldn't care less about speeding up the recovery
   process.
   
   As far as Bruce's question goes, what kind of corruption can happen to
   the log files? We write a full block at a time, I guess, so it might
   make sense to checksum it to verify that the block was not partially
   written.
   
   cjs
   -- 
   Curt Sampson  <cjs@cynic.net>   +81 90 7737 2974   http://www.netbsd.org
       Don't you know, in this new Dark Age, we're all light.  --XTC
   
   

3. Re: WAL replay logic (was Re: [PERFORM] Mount options f

   Mikheev, Vadim <vmikheev@sectordata.com> — 2003-02-19T05:31:03Z

   > > > > So if you do this, do you still need to store that information in
   > > > > pg_control at all?
   > >
   > > Yes: to "speeds up the recovery process".
   >
   > If it's going to slow down the performance of my database when not doing
   > recovery (because I have to write two files for every transaction,
   > rather than one)
   
   Control file is not updated "for every transaction", only on a few special
   events
   like checkpoint.
   
   Vadim