| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Ben Grimm <bgrimm(at)zaeon(dot)com> |
| Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, pgsql-bugs(at)postgresql(dot)org, Vadim Mikheev <vmikheev(at)sectorbase(dot)com> |
| Subject: | Re: Bug #613: Sequence values fall back to previously checkpointed |
| Date: | 2002-03-13 19:39:37 |
| Message-ID: | 10283.1016048377@sss.pgh.pa.us |
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| Lists: | pgsql-bugs |
Ben Grimm <bgrimm(at)zaeon(dot)com> writes:
> It seems like you just need to ensure that when the sequence is loaded
> from disk that log_cnt gets updated and written back to disk before the
> sequence is used. I'm not sure of the impact, but I can't reproduce the
> bugs after making these changes. I just added a flag to the SeqTableData
> struct to say whether its been logged yet - this seems like overkill..
> but it works for me :-) (at least in the scenarios I've tried)
I don't think that can work. AFAICT what your patch does is to ensure
a WAL record is written by the first nextval() in any given backend
session. But what we need is to ensure a WAL record from the first
nextval() after a checkpoint. The failure cases for your patch would
involve backends that have been running for longer than one checkpoint
cycle ...
regards, tom lane
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