Thread

1. Re: After ~Crash Sequence not correct

   Vadim Mikheev <vmikheev@sectorbase.com> — 2001-12-19T18:36:46Z

   > I have verified that killing the postmaster after a few nextval's
   > leaves things in a bad state after restart.
   > 
   > I think I see the problem: in nextval(), the sequence data written to
   > the WAL log is different from that written to the data page.  Isn't
   > that bogus?
   
   It was made to avoid WAL-loging on each nextval call, ie it should work
   like OID pre-fetching: value stored in WAL must always "exceed" values
   returned by nextval so on the after-crash-restart sequence should be
   advanced to value which was never returned by nextval (for non-cycled
   sequences). Maybe I made some mistakes in implementation?
   
   Vadim
   
   

2. Re: After ~Crash Sequence not correct

   Tom Lane <tgl@sss.pgh.pa.us> — 2001-12-19T18:48:33Z

   "Mikheev, Vadim" <vmikheev@SECTORBASE.COM> writes:
   > It was made to avoid WAL-loging on each nextval call, ie it should work
   > like OID pre-fetching: value stored in WAL must always "exceed" values
   > returned by nextval so on the after-crash-restart sequence should be
   > advanced to value which was never returned by nextval (for non-cycled
   > sequences). Maybe I made some mistakes in implementation?
   
   Oh, okay.  What I saw was that the next nextval() after restart was
   higher than what I was expecting; but that's correct given the prefetch
   behavior.
   
   But we've seen several reports wherein the value appeared to go
   backwards after a crash.
   
   Stuart, you weren't running with -F (fsync off) by any chance, were you?
   
   			regards, tom lane
   
   

3. Re: After ~Crash Sequence not correct

   Bruce Momjian <pgman@candle.pha.pa.us> — 2002-01-03T05:57:13Z

   Mikheev, Vadim wrote:
   > > I have verified that killing the postmaster after a few nextval's
   > > leaves things in a bad state after restart.
   > > 
   > > I think I see the problem: in nextval(), the sequence data written to
   > > the WAL log is different from that written to the data page.  Isn't
   > > that bogus?
   > 
   > It was made to avoid WAL-loging on each nextval call, ie it should work
   > like OID pre-fetching: value stored in WAL must always "exceed" values
   > returned by nextval so on the after-crash-restart sequence should be
   > advanced to value which was never returned by nextval (for non-cycled
   > sequences). Maybe I made some mistakes in implementation?
   
   Was this ever fixed?
   
   -- 
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